Use TestHashType in tests

...instead of calling ProtocolTraits::IsCompatible

28 files changed, 129 insertions, 227 deletions

diff --git a/test/buildtool/build_engine/base_maps/TARGETS b/test/buildtool/build_engine/base_maps/TARGETS
index bb145bac..97871ad2 100644
--- a/test/buildtool/build_engine/base_maps/TARGETS
+++ b/test/buildtool/build_engine/base_maps/TARGETS
@@ -69,6 +69,7 @@
     , ["@", "src", "src/buildtool/build_engine/base_maps", "entity_name_data"]
     , ["@", "src", "src/buildtool/file_system", "file_root"]
     , ["@", "src", "src/buildtool/crypto", "hash_function"]
+    , ["utils", "test_hash_function_type"]
     ]
   , "stage": ["test", "buildtool", "build_engine", "base_maps"]
   }
diff --git a/test/buildtool/build_engine/base_maps/source_map.test.cpp b/test/buildtool/build_engine/base_maps/source_map.test.cpp
index bd1e71ba..ab5323e4 100644
--- a/test/buildtool/build_engine/base_maps/source_map.test.cpp
+++ b/test/buildtool/build_engine/base_maps/source_map.test.cpp
@@ -32,6 +32,7 @@
 #include "src/buildtool/multithreading/async_map_consumer.hpp"
 #include "src/buildtool/multithreading/task_system.hpp"
 #include "test/buildtool/build_engine/base_maps/test_repo.hpp"
+#include "test/utils/hermeticity/test_hash_function_type.hpp"
 
 namespace {
 
@@ -89,16 +90,14 @@ auto ReadSourceTarget(EntityName const& id,
 }  // namespace
 
 TEST_CASE("from file") {
+    auto const hash_type = TestHashType::ReadFromEnvironment();
+
     nlohmann::json artifacts;
     auto name = EntityName{"", ".", "file"};
     auto consumer = [&artifacts](auto values) {
         artifacts = (*values[0])->Artifacts()->ToJson();
     };
 
-    auto const hash_type = ProtocolTraits::Instance().IsCompatible()
-                               ? HashFunction::Type::PlainSHA256
-                               : HashFunction::Type::GitSHA1;
-
     SECTION("via file") {
         CHECK(ReadSourceTarget(name, consumer, hash_type, /*use_git=*/false));
         CHECK(artifacts["file"]["type"] == "LOCAL");
@@ -108,24 +107,22 @@ TEST_CASE("from file") {
     SECTION("via git tree") {
         CHECK(ReadSourceTarget(name, consumer, hash_type, /*use_git=*/true));
         CHECK(artifacts["file"]["type"] == "KNOWN");
-        CHECK(artifacts["file"]["data"]["id"] ==
-              (ProtocolTraits::Instance().IsCompatible() ? kEmptySha256
-                                                         : kEmptySha1));
+        CHECK(
+            artifacts["file"]["data"]["id"] ==
+            (ProtocolTraits::IsNative(hash_type) ? kEmptySha1 : kEmptySha256));
         CHECK(artifacts["file"]["data"]["size"] == 0);
     }
 }
 
 TEST_CASE("not present at all") {
+    auto const hash_type = TestHashType::ReadFromEnvironment();
+
     bool consumed{false};
     bool failure_called{false};
     auto name = EntityName{"", ".", "does_not_exist"};
     auto consumer = [&consumed](auto /*unused*/) { consumed = true; };
     auto fail_func = [&failure_called]() { failure_called = true; };
 
-    auto const hash_type = ProtocolTraits::Instance().IsCompatible()
-                               ? HashFunction::Type::PlainSHA256
-                               : HashFunction::Type::GitSHA1;
-
     SECTION("via file") {
         CHECK_FALSE(ReadSourceTarget(
             name, consumer, hash_type, /*use_git=*/false, fail_func));
@@ -142,16 +139,14 @@ TEST_CASE("not present at all") {
 }
 
 TEST_CASE("malformed entry") {
+    auto const hash_type = TestHashType::ReadFromEnvironment();
+
     bool consumed{false};
     bool failure_called{false};
     auto name = EntityName{"", ".", "bad_entry"};
     auto consumer = [&consumed](auto /*unused*/) { consumed = true; };
     auto fail_func = [&failure_called]() { failure_called = true; };
 
-    auto const hash_type = ProtocolTraits::Instance().IsCompatible()
-                               ? HashFunction::Type::PlainSHA256
-                               : HashFunction::Type::GitSHA1;
-
     SECTION("via git tree") {
         CHECK_FALSE(ReadSourceTarget(
             name, consumer, hash_type, /*use_git=*/false, fail_func));
@@ -168,16 +163,14 @@ TEST_CASE("malformed entry") {
 }
 
 TEST_CASE("subdir file") {
+    auto const hash_type = TestHashType::ReadFromEnvironment();
+
     nlohmann::json artifacts;
     auto name = EntityName{"", "foo", "bar/file"};
     auto consumer = [&artifacts](auto values) {
         artifacts = (*values[0])->Artifacts()->ToJson();
     };
 
-    auto const hash_type = ProtocolTraits::Instance().IsCompatible()
-                               ? HashFunction::Type::PlainSHA256
-                               : HashFunction::Type::GitSHA1;
-
     SECTION("via file") {
         CHECK(ReadSourceTarget(name, consumer, hash_type, /*use_git=*/false));
         CHECK(artifacts["bar/file"]["type"] == "LOCAL");
@@ -187,24 +180,22 @@ TEST_CASE("subdir file") {
     SECTION("via git tree") {
         CHECK(ReadSourceTarget(name, consumer, hash_type, /*use_git=*/true));
         CHECK(artifacts["bar/file"]["type"] == "KNOWN");
-        CHECK(artifacts["bar/file"]["data"]["id"] ==
-              (ProtocolTraits::Instance().IsCompatible() ? kEmptySha256
-                                                         : kEmptySha1));
+        CHECK(
+            artifacts["bar/file"]["data"]["id"] ==
+            (ProtocolTraits::IsNative(hash_type) ? kEmptySha1 : kEmptySha256));
         CHECK(artifacts["bar/file"]["data"]["size"] == 0);
     }
 }
 
 TEST_CASE("subdir symlink") {
+    auto const hash_type = TestHashType::ReadFromEnvironment();
+
     nlohmann::json artifacts;
     auto name = EntityName{"", "foo", "link"};
     auto consumer = [&artifacts](auto values) {
         artifacts = (*values[0])->Artifacts()->ToJson();
     };
 
-    auto const hash_type = ProtocolTraits::Instance().IsCompatible()
-                               ? HashFunction::Type::PlainSHA256
-                               : HashFunction::Type::GitSHA1;
-
     SECTION("via file") {
         CHECK(ReadSourceTarget(name, consumer, hash_type, /*use_git=*/false));
         CHECK(artifacts["link"]["type"] == "LOCAL");
@@ -215,8 +206,8 @@ TEST_CASE("subdir symlink") {
         CHECK(ReadSourceTarget(name, consumer, hash_type, /*use_git=*/true));
         CHECK(artifacts["link"]["type"] == "KNOWN");
         CHECK(artifacts["link"]["data"]["id"] ==
-              (ProtocolTraits::Instance().IsCompatible() ? kSrcLinkIdSha256
-                                                         : kSrcLinkIdSha1));
+              (ProtocolTraits::IsNative(hash_type) ? kSrcLinkIdSha1
+                                                   : kSrcLinkIdSha256));
         CHECK(artifacts["link"]["data"]["size"] == 5);  // content: dummy
     }
 }
diff --git a/test/buildtool/common/TARGETS b/test/buildtool/common/TARGETS
index 1355af3f..020d0f28 100644
--- a/test/buildtool/common/TARGETS
+++ b/test/buildtool/common/TARGETS
@@ -9,9 +9,9 @@
     , ["@", "src", "src/buildtool/common", "artifact_description"]
     , ["@", "src", "src/buildtool/common", "common"]
     , ["@", "src", "src/buildtool/common", "artifact_digest_factory"]
-    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     , ["@", "src", "src/buildtool/crypto", "hash_function"]
     , ["@", "src", "src/buildtool/file_system", "object_type"]
+    , ["utils", "test_hash_function_type"]
     ]
   , "stage": ["test", "buildtool", "common"]
   }
@@ -25,8 +25,8 @@
     , ["@", "json", "", "json"]
     , ["@", "src", "src/buildtool/common", "action_description"]
     , ["@", "src", "src/buildtool/common", "common"]
-    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     , ["@", "src", "src/buildtool/crypto", "hash_function"]
+    , ["utils", "test_hash_function_type"]
     ]
   , "stage": ["test", "buildtool", "common"]
   }
diff --git a/test/buildtool/common/action_description.test.cpp b/test/buildtool/common/action_description.test.cpp
index 504f6aa3..65f5d92e 100644
--- a/test/buildtool/common/action_description.test.cpp
+++ b/test/buildtool/common/action_description.test.cpp
@@ -20,14 +20,8 @@
 #include "nlohmann/json.hpp"
 #include "src/buildtool/common/action.hpp"
 #include "src/buildtool/common/artifact_description.hpp"
-#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/crypto/hash_function.hpp"
-
-[[nodiscard]] static inline auto GetHashType(bool compatible) noexcept
-    -> HashFunction::Type {
-    return compatible ? HashFunction::Type::PlainSHA256
-                      : HashFunction::Type::GitSHA1;
-}
+#include "test/utils/hermeticity/test_hash_function_type.hpp"
 
 TEST_CASE("From JSON", "[action_description]") {
     using path = std::filesystem::path;
@@ -45,8 +39,7 @@ TEST_CASE("From JSON", "[action_description]") {
                           desc.Inputs()}
             .ToJson();
 
-    auto const hash_type =
-        GetHashType(ProtocolTraits::Instance().IsCompatible());
+    auto const hash_type = TestHashType::ReadFromEnvironment();
     SECTION("Parse full action") {
         auto description = ActionDescription::FromJson(hash_type, "id", json);
         REQUIRE(description);
diff --git a/test/buildtool/common/artifact_description.test.cpp b/test/buildtool/common/artifact_description.test.cpp
index 99a24964..44acaae6 100644
--- a/test/buildtool/common/artifact_description.test.cpp
+++ b/test/buildtool/common/artifact_description.test.cpp
@@ -22,14 +22,12 @@
 #include "src/buildtool/common/artifact.hpp"
 #include "src/buildtool/common/artifact_digest.hpp"
 #include "src/buildtool/common/artifact_digest_factory.hpp"
-#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/crypto/hash_function.hpp"
 #include "src/buildtool/file_system/object_type.hpp"
+#include "test/utils/hermeticity/test_hash_function_type.hpp"
 
 static auto NamedDigest(std::string const& str) -> ArtifactDigest {
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
     return ArtifactDigestFactory::HashDataAs<ObjectType::File>(hash_function,
                                                                str);
 }
@@ -40,18 +38,11 @@ static auto NamedDigest(std::string const& str) -> ArtifactDigest {
            lhs.Info() == rhs.Info();
 }
 
-[[nodiscard]] static inline auto GetHashType(bool compatible) noexcept
-    -> HashFunction::Type {
-    return compatible ? HashFunction::Type::PlainSHA256
-                      : HashFunction::Type::GitSHA1;
-}
-
 TEST_CASE("Local artifact", "[artifact_description]") {
     auto local_desc = ArtifactDescription::CreateLocal(
         std::filesystem::path{"local_path"}, "repo");
     auto from_json = ArtifactDescription::FromJson(
-        GetHashType(ProtocolTraits::Instance().IsCompatible()),
-        local_desc.ToJson());
+        TestHashType::ReadFromEnvironment(), local_desc.ToJson());
     CHECK(local_desc == *from_json);
 }
 
@@ -60,24 +51,21 @@ TEST_CASE("Known artifact", "[artifact_description]") {
         auto known_desc = ArtifactDescription::CreateKnown(
             NamedDigest("f_fake_hash"), ObjectType::File);
         auto from_json = ArtifactDescription::FromJson(
-            GetHashType(ProtocolTraits::Instance().IsCompatible()),
-            known_desc.ToJson());
+            TestHashType::ReadFromEnvironment(), known_desc.ToJson());
         CHECK(known_desc == *from_json);
     }
     SECTION("Executable object") {
         auto known_desc = ArtifactDescription::CreateKnown(
             NamedDigest("x_fake_hash"), ObjectType::Executable);
         auto from_json = ArtifactDescription::FromJson(
-            GetHashType(ProtocolTraits::Instance().IsCompatible()),
-            known_desc.ToJson());
+            TestHashType::ReadFromEnvironment(), known_desc.ToJson());
         CHECK(known_desc == *from_json);
     }
     SECTION("Symlink object") {
         auto known_desc = ArtifactDescription::CreateKnown(
             NamedDigest("l_fake_hash"), ObjectType::Symlink);
         auto from_json = ArtifactDescription::FromJson(
-            GetHashType(ProtocolTraits::Instance().IsCompatible()),
-            known_desc.ToJson());
+            TestHashType::ReadFromEnvironment(), known_desc.ToJson());
         CHECK(known_desc == *from_json);
     }
 }
@@ -86,8 +74,7 @@ TEST_CASE("Action artifact", "[artifact_description]") {
     auto action_desc = ArtifactDescription::CreateAction(
         "action_id", std::filesystem::path{"out_path"});
     auto from_json = ArtifactDescription::FromJson(
-        GetHashType(ProtocolTraits::Instance().IsCompatible()),
-        action_desc.ToJson());
+        TestHashType::ReadFromEnvironment(), action_desc.ToJson());
     CHECK(action_desc == *from_json);
 }
 
@@ -98,8 +85,7 @@ TEST_CASE("From JSON", "[artifact_description]") {
             .ToJson();
     auto action = ArtifactDescription::CreateAction("id", "output").ToJson();
 
-    auto const hash_type =
-        GetHashType(ProtocolTraits::Instance().IsCompatible());
+    auto const hash_type = TestHashType::ReadFromEnvironment();
     SECTION("Parse artifacts") {
         CHECK(ArtifactDescription::FromJson(hash_type, local));
         CHECK(ArtifactDescription::FromJson(hash_type, known));
@@ -177,20 +163,19 @@ TEST_CASE("From JSON", "[artifact_description]") {
 TEST_CASE("Description missing mandatory key/value pair",
           "[artifact_description]") {
     nlohmann::json const missing_type = {{"data", {{"path", "some/path"}}}};
-    CHECK(not ArtifactDescription::FromJson(
-        GetHashType(ProtocolTraits::Instance().IsCompatible()), missing_type));
+    CHECK(not ArtifactDescription::FromJson(TestHashType::ReadFromEnvironment(),
+                                            missing_type));
     nlohmann::json const missing_data = {{"type", "LOCAL"}};
-    CHECK(not ArtifactDescription::FromJson(
-        GetHashType(ProtocolTraits::Instance().IsCompatible()), missing_data));
+    CHECK(not ArtifactDescription::FromJson(TestHashType::ReadFromEnvironment(),
+                                            missing_data));
 }
 
 TEST_CASE("Local artifact description contains incorrect value for \"data\"",
           "[artifact_description]") {
     nlohmann::json const local_art_missing_path = {
         {"type", "LOCAL"}, {"data", nlohmann::json::object()}};
-    CHECK(not ArtifactDescription::FromJson(
-        GetHashType(ProtocolTraits::Instance().IsCompatible()),
-        local_art_missing_path));
+    CHECK(not ArtifactDescription::FromJson(TestHashType::ReadFromEnvironment(),
+                                            local_art_missing_path));
 }
 
 TEST_CASE("Known artifact description contains incorrect value for \"data\"",
@@ -202,24 +187,21 @@ TEST_CASE("Known artifact description contains incorrect value for \"data\"",
             {"type", "KNOWN"},
             {"data", {{"size", 15}, {"file_type", file_type}}}};
         CHECK(not ArtifactDescription::FromJson(
-            GetHashType(ProtocolTraits::Instance().IsCompatible()),
-            known_art_missing_id));
+            TestHashType::ReadFromEnvironment(), known_art_missing_id));
     }
     SECTION("missing \"size\"") {
         nlohmann::json const known_art_missing_size = {
             {"type", "KNOWN"},
             {"data", {{"id", "known_input"}, {"file_type", file_type}}}};
         CHECK(not ArtifactDescription::FromJson(
-            GetHashType(ProtocolTraits::Instance().IsCompatible()),
-            known_art_missing_size));
+            TestHashType::ReadFromEnvironment(), known_art_missing_size));
     }
     SECTION("missing \"file_type\"") {
         nlohmann::json const known_art_missing_file_type = {
             {"type", "KNOWN"}, {"data", {{"id", "known_input"}, {"size", 15}}}};
 
         CHECK(not ArtifactDescription::FromJson(
-            GetHashType(ProtocolTraits::Instance().IsCompatible()),
-            known_art_missing_file_type));
+            TestHashType::ReadFromEnvironment(), known_art_missing_file_type));
     }
 }
 
@@ -227,13 +209,11 @@ TEST_CASE("Action artifact description contains incorrect value for \"data\"",
           "[artifact_description]") {
     nlohmann::json const action_art_missing_id = {
         {"type", "ACTION"}, {"data", {{"path", "output/path"}}}};
-    CHECK(not ArtifactDescription::FromJson(
-        GetHashType(ProtocolTraits::Instance().IsCompatible()),
-        action_art_missing_id));
+    CHECK(not ArtifactDescription::FromJson(TestHashType::ReadFromEnvironment(),
+                                            action_art_missing_id));
 
     nlohmann::json const action_art_missing_path = {
         {"type", "ACTION"}, {"data", {{"id", "action_id"}}}};
-    CHECK(not ArtifactDescription::FromJson(
-        GetHashType(ProtocolTraits::Instance().IsCompatible()),
-        action_art_missing_path));
+    CHECK(not ArtifactDescription::FromJson(TestHashType::ReadFromEnvironment(),
+                                            action_art_missing_path));
 }
diff --git a/test/buildtool/execution_api/bazel/TARGETS b/test/buildtool/execution_api/bazel/TARGETS
index 64e52ad6..02b55b78 100644
--- a/test/buildtool/execution_api/bazel/TARGETS
+++ b/test/buildtool/execution_api/bazel/TARGETS
@@ -9,13 +9,13 @@
     , ["utils", "test_auth_config"]
     , ["utils", "test_remote_config"]
     , ["@", "src", "src/buildtool/common", "bazel_digest_factory"]
-    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     , ["@", "src", "src/buildtool/common/remote", "retry_config"]
     , ["@", "src", "src/buildtool/execution_api/bazel_msg", "bazel_msg"]
     , ["@", "src", "src/buildtool/execution_api/remote", "bazel_network"]
     , ["@", "src", "src/buildtool/execution_api/remote", "config"]
     , ["@", "src", "src/buildtool/file_system", "object_type"]
     , ["@", "src", "src/buildtool/crypto", "hash_function"]
+    , ["utils", "test_hash_function_type"]
     ]
   , "stage": ["test", "buildtool", "execution_api", "bazel"]
   }
@@ -30,12 +30,12 @@
     , ["utils", "test_auth_config"]
     , ["utils", "test_remote_config"]
     , ["@", "src", "src/buildtool/common", "bazel_digest_factory"]
-    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     , ["@", "src", "src/buildtool/common/remote", "retry_config"]
     , ["@", "src", "src/buildtool/execution_api/remote", "bazel_network"]
     , ["@", "src", "src/buildtool/execution_api/remote", "config"]
     , ["@", "src", "src/buildtool/file_system", "object_type"]
     , ["@", "src", "src/buildtool/crypto", "hash_function"]
+    , ["utils", "test_hash_function_type"]
     ]
   , "stage": ["test", "buildtool", "execution_api", "bazel"]
   }
@@ -50,12 +50,12 @@
     , ["utils", "test_auth_config"]
     , ["utils", "test_remote_config"]
     , ["@", "src", "src/buildtool/common", "bazel_digest_factory"]
-    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     , ["@", "src", "src/buildtool/execution_api/bazel_msg", "bazel_msg"]
     , ["@", "src", "src/buildtool/execution_api/remote", "bazel_network"]
     , ["@", "src", "src/buildtool/execution_api/remote", "config"]
     , ["@", "src", "src/buildtool/file_system", "object_type"]
     , ["@", "src", "src/buildtool/crypto", "hash_function"]
+    , ["utils", "test_hash_function_type"]
     ]
   , "stage": ["test", "buildtool", "execution_api", "bazel"]
   }
@@ -77,6 +77,7 @@
     , ["@", "src", "src/buildtool/execution_api/remote", "config"]
     , ["@", "src", "src/buildtool/file_system", "object_type"]
     , ["@", "src", "src/buildtool/crypto", "hash_function"]
+    , ["utils", "test_hash_function_type"]
     ]
   , "stage": ["test", "buildtool", "execution_api", "bazel"]
   }
@@ -97,8 +98,8 @@
     , ["@", "src", "src/buildtool/file_system", "object_type"]
     , ["@", "src", "src/buildtool/common", "common"]
     , ["@", "src", "src/buildtool/common", "artifact_digest_factory"]
-    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     , ["@", "src", "src/buildtool/crypto", "hash_function"]
+    , ["utils", "test_hash_function_type"]
     , ["@", "src", "src/buildtool/execution_api/common", "common"]
     , [ "@"
       , "src"
@@ -122,7 +123,7 @@
     , ["@", "src", "src/buildtool/execution_api/remote", "bazel"]
     , ["buildtool/execution_api/common", "api_test"]
     , ["@", "src", "src/buildtool/crypto", "hash_function"]
-    , ["@", "src", "src/buildtool/common", "protocol_traits"]
+    , ["utils", "test_hash_function_type"]
     ]
   , "stage": ["test", "buildtool", "execution_api", "bazel"]
   }
diff --git a/test/buildtool/execution_api/bazel/bazel_api.test.cpp b/test/buildtool/execution_api/bazel/bazel_api.test.cpp
index 5dc4198d..16c45aae 100644
--- a/test/buildtool/execution_api/bazel/bazel_api.test.cpp
+++ b/test/buildtool/execution_api/bazel/bazel_api.test.cpp
@@ -18,11 +18,11 @@
 #include <string>
 
 #include "catch2/catch_test_macros.hpp"
-#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/common/remote/retry_config.hpp"
 #include "src/buildtool/crypto/hash_function.hpp"
 #include "src/buildtool/execution_api/remote/config.hpp"
 #include "test/buildtool/execution_api/common/api_test.hpp"
+#include "test/utils/hermeticity/test_hash_function_type.hpp"
 #include "test/utils/remote_execution/test_auth_config.hpp"
 #include "test/utils/remote_execution/test_remote_config.hpp"
 
@@ -59,15 +59,13 @@ class FactoryApi final {
 
 TEST_CASE("BazelAPI: No input, no output", "[execution_api]") {
     auto remote_config = TestRemoteConfig::ReadFromEnvironment();
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
+
     REQUIRE(remote_config);
     REQUIRE(remote_config->remote_address);
     auto auth = TestAuthConfig::ReadFromEnvironment();
     REQUIRE(auth);
 
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
-
     FactoryApi api_factory{
         &*remote_config->remote_address, &*auth, hash_function};
     TestNoInputNoOutput(api_factory, remote_config->platform_properties);
@@ -75,15 +73,13 @@ TEST_CASE("BazelAPI: No input, no output", "[execution_api]") {
 
 TEST_CASE("BazelAPI: No input, create output", "[execution_api]") {
     auto remote_config = TestRemoteConfig::ReadFromEnvironment();
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
+
     REQUIRE(remote_config);
     REQUIRE(remote_config->remote_address);
     auto auth = TestAuthConfig::ReadFromEnvironment();
     REQUIRE(auth);
 
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
-
     FactoryApi api_factory{
         &*remote_config->remote_address, &*auth, hash_function};
     TestNoInputCreateOutput(api_factory, remote_config->platform_properties);
@@ -91,15 +87,13 @@ TEST_CASE("BazelAPI: No input, create output", "[execution_api]") {
 
 TEST_CASE("BazelAPI: One input copied to output", "[execution_api]") {
     auto remote_config = TestRemoteConfig::ReadFromEnvironment();
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
+
     REQUIRE(remote_config);
     REQUIRE(remote_config->remote_address);
     auto auth = TestAuthConfig::ReadFromEnvironment();
     REQUIRE(auth);
 
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
-
     FactoryApi api_factory{
         &*remote_config->remote_address, &*auth, hash_function};
     TestOneInputCopiedToOutput(api_factory, remote_config->platform_properties);
@@ -107,15 +101,13 @@ TEST_CASE("BazelAPI: One input copied to output", "[execution_api]") {
 
 TEST_CASE("BazelAPI: Non-zero exit code, create output", "[execution_api]") {
     auto remote_config = TestRemoteConfig::ReadFromEnvironment();
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
+
     REQUIRE(remote_config);
     REQUIRE(remote_config->remote_address);
     auto auth = TestAuthConfig::ReadFromEnvironment();
     REQUIRE(auth);
 
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
-
     FactoryApi api_factory{
         &*remote_config->remote_address, &*auth, hash_function};
     TestNonZeroExitCodeCreateOutput(api_factory,
@@ -124,15 +116,13 @@ TEST_CASE("BazelAPI: Non-zero exit code, create output", "[execution_api]") {
 
 TEST_CASE("BazelAPI: Retrieve two identical trees to path", "[execution_api]") {
     auto remote_config = TestRemoteConfig::ReadFromEnvironment();
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
+
     REQUIRE(remote_config);
     REQUIRE(remote_config->remote_address);
     auto auth = TestAuthConfig::ReadFromEnvironment();
     REQUIRE(auth);
 
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
-
     FactoryApi api_factory{
         &*remote_config->remote_address, &*auth, hash_function};
     TestRetrieveTwoIdenticalTreesToPath(
@@ -142,15 +132,13 @@ TEST_CASE("BazelAPI: Retrieve two identical trees to path", "[execution_api]") {
 TEST_CASE("BazelAPI: Retrieve file and symlink with same content to path",
           "[execution_api]") {
     auto remote_config = TestRemoteConfig::ReadFromEnvironment();
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
+
     REQUIRE(remote_config);
     REQUIRE(remote_config->remote_address);
     auto auth = TestAuthConfig::ReadFromEnvironment();
     REQUIRE(auth);
 
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
-
     FactoryApi api_factory{
         &*remote_config->remote_address, &*auth, hash_function};
     TestRetrieveFileAndSymlinkWithSameContentToPath(
@@ -159,15 +147,13 @@ TEST_CASE("BazelAPI: Retrieve file and symlink with same content to path",
 
 TEST_CASE("BazelAPI: Retrieve mixed blobs and trees", "[execution_api]") {
     auto remote_config = TestRemoteConfig::ReadFromEnvironment();
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
+
     REQUIRE(remote_config);
     REQUIRE(remote_config->remote_address);
     auto auth = TestAuthConfig::ReadFromEnvironment();
     REQUIRE(auth);
 
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
-
     FactoryApi api_factory{
         &*remote_config->remote_address, &*auth, hash_function};
     TestRetrieveMixedBlobsAndTrees(
@@ -176,15 +162,13 @@ TEST_CASE("BazelAPI: Retrieve mixed blobs and trees", "[execution_api]") {
 
 TEST_CASE("BazelAPI: Create directory prior to execution", "[execution_api]") {
     auto remote_config = TestRemoteConfig::ReadFromEnvironment();
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
+
     REQUIRE(remote_config);
     REQUIRE(remote_config->remote_address);
     auto auth = TestAuthConfig::ReadFromEnvironment();
     REQUIRE(auth);
 
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
-
     FactoryApi api_factory{
         &*remote_config->remote_address, &*auth, hash_function};
     TestCreateDirPriorToExecution(api_factory,
diff --git a/test/buildtool/execution_api/bazel/bazel_cas_client.test.cpp b/test/buildtool/execution_api/bazel/bazel_cas_client.test.cpp
index 4be61071..e8234282 100644
--- a/test/buildtool/execution_api/bazel/bazel_cas_client.test.cpp
+++ b/test/buildtool/execution_api/bazel/bazel_cas_client.test.cpp
@@ -21,13 +21,13 @@
 #include "catch2/catch_test_macros.hpp"
 #include "gsl/gsl"
 #include "src/buildtool/common/bazel_digest_factory.hpp"
-#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/common/remote/retry_config.hpp"
 #include "src/buildtool/crypto/hash_function.hpp"
 #include "src/buildtool/execution_api/bazel_msg/bazel_blob_container.hpp"
 #include "src/buildtool/execution_api/remote/bazel/bazel_execution_client.hpp"
 #include "src/buildtool/execution_api/remote/config.hpp"
 #include "src/buildtool/file_system/object_type.hpp"
+#include "test/utils/hermeticity/test_hash_function_type.hpp"
 #include "test/utils/remote_execution/test_auth_config.hpp"
 #include "test/utils/remote_execution/test_remote_config.hpp"
 
@@ -50,10 +50,7 @@ TEST_CASE("Bazel internals: CAS Client", "[execution_api]") {
 
     SECTION("Valid digest and blob") {
         // digest of "test"
-        HashFunction const hash_function{
-            ProtocolTraits::Instance().IsCompatible()
-                ? HashFunction::Type::PlainSHA256
-                : HashFunction::Type::GitSHA1};
+        HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
         auto digest = BazelDigestFactory::HashDataAs<ObjectType::File>(
             hash_function, content);
 
diff --git a/test/buildtool/execution_api/bazel/bazel_execution_client.test.cpp b/test/buildtool/execution_api/bazel/bazel_execution_client.test.cpp
index a0f77066..e7df319b 100644
--- a/test/buildtool/execution_api/bazel/bazel_execution_client.test.cpp
+++ b/test/buildtool/execution_api/bazel/bazel_execution_client.test.cpp
@@ -18,11 +18,11 @@
 
 #include "catch2/catch_test_macros.hpp"
 #include "src/buildtool/common/bazel_digest_factory.hpp"
-#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/common/remote/retry_config.hpp"
 #include "src/buildtool/crypto/hash_function.hpp"
 #include "src/buildtool/execution_api/remote/config.hpp"
 #include "src/buildtool/file_system/object_type.hpp"
+#include "test/utils/hermeticity/test_hash_function_type.hpp"
 #include "test/utils/remote_execution/bazel_action_creator.hpp"
 #include "test/utils/remote_execution/test_auth_config.hpp"
 #include "test/utils/remote_execution/test_remote_config.hpp"
@@ -31,9 +31,7 @@ TEST_CASE("Bazel internals: Execution Client", "[execution_api]") {
     std::string instance_name{"remote-execution"};
     std::string content("test");
 
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
 
     auto test_digest = BazelDigestFactory::HashDataAs<ObjectType::File>(
         hash_function, content);
@@ -115,9 +113,7 @@ TEST_CASE("Bazel internals: Execution Client using env variables",
     std::string instance_name{"remote-execution"};
     std::string content("contents of env variable");
 
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
 
     auto test_digest = BazelDigestFactory::HashDataAs<ObjectType::File>(
         hash_function, content);
diff --git a/test/buildtool/execution_api/bazel/bazel_msg_factory.test.cpp b/test/buildtool/execution_api/bazel/bazel_msg_factory.test.cpp
index 8ec074f9..5262971c 100644
--- a/test/buildtool/execution_api/bazel/bazel_msg_factory.test.cpp
+++ b/test/buildtool/execution_api/bazel/bazel_msg_factory.test.cpp
@@ -23,11 +23,11 @@
 #include "src/buildtool/common/artifact_description.hpp"
 #include "src/buildtool/common/artifact_digest.hpp"
 #include "src/buildtool/common/artifact_digest_factory.hpp"
-#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/crypto/hash_function.hpp"
 #include "src/buildtool/execution_api/common/artifact_blob_container.hpp"
 #include "src/buildtool/file_system/file_system_manager.hpp"
 #include "src/buildtool/file_system/object_type.hpp"
+#include "test/utils/hermeticity/test_hash_function_type.hpp"
 
 namespace {
 /// \brief Create a blob from the content found in file or symlink pointed to by
@@ -62,9 +62,7 @@ TEST_CASE("Bazel internals: MessageFactory", "[execution_api]") {
     std::filesystem::path link = subdir1 / "link";
     REQUIRE(FileSystemManager::CreateSymlink("file1", link));
 
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
 
     // create the corresponding blobs
     auto file1_blob = CreateBlobFromPath(file1, hash_function);
diff --git a/test/buildtool/execution_api/bazel/bazel_network.test.cpp b/test/buildtool/execution_api/bazel/bazel_network.test.cpp
index c69e7619..8224de74 100644
--- a/test/buildtool/execution_api/bazel/bazel_network.test.cpp
+++ b/test/buildtool/execution_api/bazel/bazel_network.test.cpp
@@ -29,6 +29,7 @@
 #include "src/buildtool/execution_api/remote/bazel/bazel_execution_client.hpp"
 #include "src/buildtool/execution_api/remote/config.hpp"
 #include "src/buildtool/file_system/object_type.hpp"
+#include "test/utils/hermeticity/test_hash_function_type.hpp"
 #include "test/utils/remote_execution/test_auth_config.hpp"
 #include "test/utils/remote_execution/test_remote_config.hpp"
 
@@ -46,9 +47,7 @@ TEST_CASE("Bazel network: write/read blobs", "[execution_api]") {
 
     RetryConfig retry_config{};  // default retry config
 
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
 
     auto network = BazelNetwork{instance_name,
                                 remote_config->remote_address->host,
@@ -97,7 +96,8 @@ TEST_CASE("Bazel network: write/read blobs", "[execution_api]") {
 }
 
 TEST_CASE("Bazel network: read blobs with unknown size", "[execution_api]") {
-    if (ProtocolTraits::Instance().IsCompatible()) {
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
+    if (not ProtocolTraits::IsNative(hash_function.GetType())) {
         // only supported in native mode
         return;
     }
@@ -113,10 +113,6 @@ TEST_CASE("Bazel network: read blobs with unknown size", "[execution_api]") {
 
     RetryConfig retry_config{};  // default retry config
 
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
-
     auto network = BazelNetwork{instance_name,
                                 remote_config->remote_address->host,
                                 remote_config->remote_address->port,
diff --git a/test/buildtool/execution_api/bazel/bytestream_client.test.cpp b/test/buildtool/execution_api/bazel/bytestream_client.test.cpp
index 1956a6a3..c8b7cac6 100644
--- a/test/buildtool/execution_api/bazel/bytestream_client.test.cpp
+++ b/test/buildtool/execution_api/bazel/bytestream_client.test.cpp
@@ -21,12 +21,12 @@
 #include "catch2/catch_test_macros.hpp"
 #include "src/buildtool/auth/authentication.hpp"
 #include "src/buildtool/common/bazel_digest_factory.hpp"
-#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/crypto/hash_function.hpp"
 #include "src/buildtool/execution_api/bazel_msg/bazel_blob_container.hpp"
 #include "src/buildtool/execution_api/common/execution_common.hpp"
 #include "src/buildtool/execution_api/remote/config.hpp"
 #include "src/buildtool/file_system/object_type.hpp"
+#include "test/utils/hermeticity/test_hash_function_type.hpp"
 #include "test/utils/remote_execution/test_auth_config.hpp"
 #include "test/utils/remote_execution/test_remote_config.hpp"
 
@@ -45,9 +45,7 @@ TEST_CASE("ByteStream Client: Transfer single blob", "[execution_api]") {
                                    &*auth_config};
     auto uuid = CreateUUIDVersion4(*CreateProcessUniqueId());
 
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
 
     SECTION("Upload small blob") {
         std::string instance_name{"remote-execution"};
@@ -152,9 +150,7 @@ TEST_CASE("ByteStream Client: Transfer multiple blobs", "[execution_api]") {
                                    &*auth_config};
     auto uuid = CreateUUIDVersion4(*CreateProcessUniqueId());
 
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
 
     SECTION("Upload small blobs") {
         std::string instance_name{"remote-execution"};
diff --git a/test/buildtool/execution_api/common/TARGETS b/test/buildtool/execution_api/common/TARGETS
index f58bb4f0..6a7dff89 100644
--- a/test/buildtool/execution_api/common/TARGETS
+++ b/test/buildtool/execution_api/common/TARGETS
@@ -5,7 +5,6 @@
   , "deps":
     [ ["@", "catch2", "", "catch2"]
     , ["@", "src", "src/buildtool/common", "artifact_description"]
-    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     , ["@", "src", "src/buildtool/common", "artifact_digest_factory"]
     , ["@", "src", "src/buildtool/execution_api/common", "common"]
     , ["@", "src", "src/buildtool/execution_api/local", "config"]
@@ -13,6 +12,7 @@
     , ["@", "src", "src/buildtool/logging", "log_level"]
     , ["@", "src", "src/buildtool/logging", "logging"]
     , ["@", "src", "src/buildtool/crypto", "hash_function"]
+    , ["utils", "test_hash_function_type"]
     ]
   , "stage": ["test", "buildtool", "execution_api", "common"]
   }
diff --git a/test/buildtool/execution_api/common/api_test.hpp b/test/buildtool/execution_api/common/api_test.hpp
index 3c4052b3..4b84d66a 100644
--- a/test/buildtool/execution_api/common/api_test.hpp
+++ b/test/buildtool/execution_api/common/api_test.hpp
@@ -25,7 +25,6 @@
 #include "catch2/catch_test_macros.hpp"
 #include "src/buildtool/common/artifact_description.hpp"
 #include "src/buildtool/common/artifact_digest_factory.hpp"
-#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/crypto/hash_function.hpp"
 #include "src/buildtool/execution_api/common/execution_action.hpp"
 #include "src/buildtool/execution_api/common/execution_api.hpp"
@@ -34,6 +33,7 @@
 #include "src/buildtool/file_system/file_system_manager.hpp"
 #include "src/buildtool/logging/log_level.hpp"
 #include "src/buildtool/logging/logger.hpp"
+#include "test/utils/hermeticity/test_hash_function_type.hpp"
 
 using ApiFactory = std::function<IExecutionApi::Ptr()>;
 using ExecProps = std::map<std::string, std::string>;
@@ -140,9 +140,7 @@ using ExecProps = std::map<std::string, std::string>;
     bool is_hermetic = false) {
     std::string test_content("test");
 
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
 
     auto test_digest = ArtifactDigestFactory::HashDataAs<ObjectType::File>(
         hash_function, test_content);
@@ -224,9 +222,7 @@ using ExecProps = std::map<std::string, std::string>;
     bool is_hermetic = false) {
     std::string test_content("test");
 
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
 
     auto test_digest = ArtifactDigestFactory::HashDataAs<ObjectType::File>(
         hash_function, test_content);
@@ -315,9 +311,7 @@ using ExecProps = std::map<std::string, std::string>;
     ExecProps const& props) {
     std::string test_content("test");
 
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
 
     auto test_digest = ArtifactDigestFactory::HashDataAs<ObjectType::File>(
         hash_function, test_content);
diff --git a/test/buildtool/execution_api/execution_service/TARGETS b/test/buildtool/execution_api/execution_service/TARGETS
index 776f0f2b..2c935848 100644
--- a/test/buildtool/execution_api/execution_service/TARGETS
+++ b/test/buildtool/execution_api/execution_service/TARGETS
@@ -21,6 +21,7 @@
     , ["@", "src", "src/buildtool/storage", "config"]
     , ["@", "src", "src/buildtool/storage", "storage"]
     , ["@", "gsl", "", "gsl"]
+    , ["utils", "test_hash_function_type"]
     ]
   , "stage": ["test", "buildtool", "execution_api", "execution_service"]
   }
diff --git a/test/buildtool/execution_api/execution_service/cas_server.test.cpp b/test/buildtool/execution_api/execution_service/cas_server.test.cpp
index 8d68d9cb..af5a3d58 100644
--- a/test/buildtool/execution_api/execution_service/cas_server.test.cpp
+++ b/test/buildtool/execution_api/execution_service/cas_server.test.cpp
@@ -27,6 +27,7 @@
 #include "src/buildtool/file_system/object_type.hpp"
 #include "src/buildtool/storage/config.hpp"
 #include "src/buildtool/storage/storage.hpp"
+#include "test/utils/hermeticity/test_hash_function_type.hpp"
 #include "test/utils/hermeticity/test_storage_config.hpp"
 
 namespace {
@@ -48,7 +49,7 @@ namespace {
 
 TEST_CASE("CAS Service: upload incomplete tree", "[execution_service]") {
     // For compatible mode tree invariants aren't checked.
-    if (ProtocolTraits::Instance().IsCompatible()) {
+    if (not ProtocolTraits::IsNative(TestHashType::ReadFromEnvironment())) {
         return;
     }
 
diff --git a/test/buildtool/execution_engine/executor/TARGETS b/test/buildtool/execution_engine/executor/TARGETS
index 74247e49..bb86c6d8 100644
--- a/test/buildtool/execution_engine/executor/TARGETS
+++ b/test/buildtool/execution_engine/executor/TARGETS
@@ -7,7 +7,6 @@
     , ["@", "src", "src/buildtool/common", "artifact_description"]
     , ["@", "src", "src/buildtool/common", "common"]
     , ["@", "src", "src/buildtool/common", "artifact_digest_factory"]
-    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     , ["@", "src", "src/buildtool/execution_api/common", "common"]
     , ["@", "src", "src/buildtool/execution_api/remote", "config"]
     , ["@", "src", "src/buildtool/execution_api/remote", "context"]
@@ -21,6 +20,7 @@
     , ["@", "gsl", "", "gsl"]
     , ["utils", "test_api_bundle"]
     , ["utils", "test_remote_config"]
+    , ["utils", "test_hash_function_type"]
     ]
   , "stage": ["test", "buildtool", "execution_engine", "executor"]
   }
@@ -34,7 +34,6 @@
     , ["@", "src", "src/buildtool/common", "common"]
     , ["@", "src", "src/buildtool/common", "artifact_digest_factory"]
     , ["@", "src", "src/buildtool/common", "config"]
-    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     , ["@", "src", "src/buildtool/common/remote", "retry_config"]
     , ["@", "src", "src/buildtool/execution_api/common", "common"]
     , ["@", "src", "src/buildtool/execution_api/remote", "config"]
@@ -48,6 +47,7 @@
     , ["@", "catch2", "", "catch2"]
     , ["@", "gsl", "", "gsl"]
     , ["utils", "test_api_bundle"]
+    , ["utils", "test_hash_function_type"]
     ]
   , "stage": ["test", "buildtool", "execution_engine", "executor"]
   }
@@ -84,7 +84,6 @@
     [ "executor_api_tests"
     , ["@", "src", "src/buildtool/common", "common"]
     , ["@", "src", "src/buildtool/common", "config"]
-    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     , ["@", "src", "src/buildtool/common/remote", "retry_config"]
     , ["@", "src", "src/buildtool/execution_api/remote", "bazel"]
     , ["@", "src", "src/buildtool/execution_api/remote", "config"]
@@ -95,6 +94,7 @@
     , ["utils", "test_auth_config"]
     , ["utils", "test_remote_config"]
     , ["@", "catch2", "", "catch2"]
+    , ["utils", "test_hash_function_type"]
     ]
   , "stage": ["test", "buildtool", "execution_engine", "executor"]
   }
diff --git a/test/buildtool/execution_engine/executor/executor.test.cpp b/test/buildtool/execution_engine/executor/executor.test.cpp
index d0533f9c..48bcf082 100644
--- a/test/buildtool/execution_engine/executor/executor.test.cpp
+++ b/test/buildtool/execution_engine/executor/executor.test.cpp
@@ -29,7 +29,6 @@
 #include "src/buildtool/common/artifact_description.hpp"
 #include "src/buildtool/common/artifact_digest.hpp"
 #include "src/buildtool/common/artifact_digest_factory.hpp"
-#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/common/repository_config.hpp"
 #include "src/buildtool/common/statistics.hpp"
 #include "src/buildtool/crypto/hash_function.hpp"
@@ -40,6 +39,7 @@
 #include "src/buildtool/file_system/file_system_manager.hpp"
 #include "src/buildtool/progress_reporting/progress.hpp"
 #include "test/utils/executor/test_api_bundle.hpp"
+#include "test/utils/hermeticity/test_hash_function_type.hpp"
 
 /// \brief Mockup API test config.
 struct TestApiConfig {
@@ -64,9 +64,7 @@ struct TestApiConfig {
 };
 
 static auto NamedDigest(std::string const& str) -> ArtifactDigest {
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
     return ArtifactDigestFactory::HashDataAs<ObjectType::File>(hash_function,
                                                                str);
 }
@@ -305,9 +303,7 @@ TEST_CASE("Executor: Process artifact", "[executor]") {
     DependencyGraph g;
     auto [config, repo_config] = CreateTest(&g, workspace_path);
 
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
 
     auto const local_cpp_id =
         ArtifactDescription::CreateLocal("local.cpp", "").Id();
@@ -383,9 +379,7 @@ TEST_CASE("Executor: Process action", "[executor]") {
     DependencyGraph g;
     auto [config, repo_config] = CreateTest(&g, workspace_path);
 
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
 
     auto const local_cpp_id =
         ArtifactDescription::CreateLocal("local.cpp", "").Id();
diff --git a/test/buildtool/execution_engine/executor/executor_api.test.hpp b/test/buildtool/execution_engine/executor/executor_api.test.hpp
index 570c6e39..c323bde6 100644
--- a/test/buildtool/execution_engine/executor/executor_api.test.hpp
+++ b/test/buildtool/execution_engine/executor/executor_api.test.hpp
@@ -27,7 +27,6 @@
 #include "src/buildtool/common/artifact.hpp"
 #include "src/buildtool/common/artifact_description.hpp"
 #include "src/buildtool/common/artifact_digest_factory.hpp"
-#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/common/remote/retry_config.hpp"
 #include "src/buildtool/common/repository_config.hpp"
 #include "src/buildtool/common/statistics.hpp"
@@ -41,6 +40,7 @@
 #include "src/buildtool/file_system/file_system_manager.hpp"
 #include "src/buildtool/progress_reporting/progress.hpp"
 #include "test/utils/executor/test_api_bundle.hpp"
+#include "test/utils/hermeticity/test_hash_function_type.hpp"
 #include "test/utils/remote_execution/test_remote_config.hpp"
 
 using ApiFactory = std::function<IExecutionApi::Ptr()>;
@@ -56,9 +56,7 @@ static inline void RunBlobUpload(RepositoryConfig* repo_config,
                                  ApiFactory const& factory) {
     SetupConfig(repo_config);
     auto api = factory();
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
 
     std::string const blob = "test";
     CHECK(api->Upload(ArtifactBlobContainer{
@@ -144,9 +142,7 @@ static inline void RunHelloWorldCompilation(
                                        .retry_config = &retry_config,
                                        .exec_config = &*remote_config};
 
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
 
     auto api = factory();
     auto const apis = CreateTestApiBundle(hash_function, api);
@@ -279,9 +275,7 @@ static inline void RunGreeterCompilation(
                                        .retry_config = &retry_config,
                                        .exec_config = &*remote_config};
 
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
 
     auto api = factory();
     auto const apis = CreateTestApiBundle(hash_function, api);
@@ -420,9 +414,7 @@ static inline void TestUploadAndDownloadTrees(
         env.emplace("PATH", "/bin:/usr/bin");
     }
 
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
 
     auto foo = std::string{"foo"};
     auto bar = std::string{"bar"};
@@ -576,9 +568,7 @@ static inline void TestRetrieveOutputDirectories(
     int /*expected_cached*/ = 0) {
     SetupConfig(repo_config);
 
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
 
     auto const make_tree_id = std::string{"make_tree"};
     auto const* make_tree_cmd =
diff --git a/test/buildtool/execution_engine/executor/executor_api_remote_bazel.test.cpp b/test/buildtool/execution_engine/executor/executor_api_remote_bazel.test.cpp
index fd2167a7..f024941c 100644
--- a/test/buildtool/execution_engine/executor/executor_api_remote_bazel.test.cpp
+++ b/test/buildtool/execution_engine/executor/executor_api_remote_bazel.test.cpp
@@ -15,7 +15,6 @@
 #include <optional>
 
 #include "catch2/catch_test_macros.hpp"
-#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/common/remote/retry_config.hpp"
 #include "src/buildtool/common/repository_config.hpp"
 #include "src/buildtool/common/statistics.hpp"
@@ -25,6 +24,7 @@
 #include "src/buildtool/execution_engine/executor/executor.hpp"
 #include "src/buildtool/progress_reporting/progress.hpp"
 #include "test/buildtool/execution_engine/executor/executor_api.test.hpp"
+#include "test/utils/hermeticity/test_hash_function_type.hpp"
 #include "test/utils/remote_execution/test_auth_config.hpp"
 #include "test/utils/remote_execution/test_remote_config.hpp"
 
@@ -41,9 +41,7 @@ TEST_CASE("Executor<BazelApi>: Upload blob", "[executor]") {
 
     RetryConfig retry_config{};  // default retry config
 
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
 
     TestBlobUpload(&repo_config, [&] {
         return BazelApi::Ptr{new BazelApi{"remote-execution",
@@ -72,9 +70,7 @@ TEST_CASE("Executor<BazelApi>: Compile hello world", "[executor]") {
 
     RetryConfig retry_config{};  // default retry config
 
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
 
     TestHelloWorldCompilation(
         &repo_config,
@@ -110,9 +106,7 @@ TEST_CASE("Executor<BazelApi>: Compile greeter", "[executor]") {
 
     RetryConfig retry_config{};  // default retry config
 
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
 
     TestGreeterCompilation(
         &repo_config,
@@ -148,9 +142,7 @@ TEST_CASE("Executor<BazelApi>: Upload and download trees", "[executor]") {
 
     RetryConfig retry_config{};  // default retry config
 
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
 
     TestUploadAndDownloadTrees(
         &repo_config,
@@ -186,9 +178,7 @@ TEST_CASE("Executor<BazelApi>: Retrieve output directories", "[executor]") {
 
     RetryConfig retry_config{};  // default retry config
 
-    HashFunction const hash_function{ProtocolTraits::Instance().IsCompatible()
-                                         ? HashFunction::Type::PlainSHA256
-                                         : HashFunction::Type::GitSHA1};
+    HashFunction const hash_function{TestHashType::ReadFromEnvironment()};
 
     TestRetrieveOutputDirectories(
         &repo_config,
diff --git a/test/buildtool/execution_engine/traverser/TARGETS b/test/buildtool/execution_engine/traverser/TARGETS
index 7228b0af..72a7abea 100644
--- a/test/buildtool/execution_engine/traverser/TARGETS
+++ b/test/buildtool/execution_engine/traverser/TARGETS
@@ -7,11 +7,11 @@
     , ["", "catch-main"]
     , ["utils", "container_matchers"]
     , ["@", "src", "src/buildtool/common", "common"]
-    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     , ["@", "src", "src/buildtool/common", "artifact_description"]
     , ["@", "src", "src/buildtool/execution_engine/dag", "dag"]
     , ["@", "src", "src/buildtool/execution_engine/traverser", "traverser"]
     , ["@", "src", "src/buildtool/crypto", "hash_function"]
+    , ["utils", "test_hash_function_type"]
     ]
   , "stage": ["test", "buildtool", "execution_engine", "traverser"]
   }
diff --git a/test/buildtool/execution_engine/traverser/traverser.test.cpp b/test/buildtool/execution_engine/traverser/traverser.test.cpp
index 7b2e6293..cc5c22e9 100644
--- a/test/buildtool/execution_engine/traverser/traverser.test.cpp
+++ b/test/buildtool/execution_engine/traverser/traverser.test.cpp
@@ -24,10 +24,10 @@
 
 #include "catch2/catch_test_macros.hpp"
 #include "src/buildtool/common/artifact_description.hpp"
-#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/crypto/hash_function.hpp"
 #include "src/buildtool/execution_engine/dag/dag.hpp"
 #include "test/utils/container_matchers.hpp"
+#include "test/utils/hermeticity/test_hash_function_type.hpp"
 
 namespace {
 
@@ -184,9 +184,7 @@ class TestProject {
         auto inputs_desc = ActionDescription::inputs_t{};
         if (not inputs.empty()) {
             command.emplace_back("FROM");
-            auto const hash_type = ProtocolTraits::Instance().IsCompatible()
-                                       ? HashFunction::Type::PlainSHA256
-                                       : HashFunction::Type::GitSHA1;
+            auto const hash_type = TestHashType::ReadFromEnvironment();
             for (auto const& input_desc : inputs) {
                 auto artifact =
                     ArtifactDescription::FromJson(hash_type, input_desc);
diff --git a/test/buildtool/file_system/TARGETS b/test/buildtool/file_system/TARGETS
index eda8f376..8d1a5c0a 100644
--- a/test/buildtool/file_system/TARGETS
+++ b/test/buildtool/file_system/TARGETS
@@ -62,11 +62,11 @@
     , ["@", "src", "src/buildtool/common", "artifact_description"]
     , ["@", "src", "src/buildtool/common", "common"]
     , ["@", "src", "src/buildtool/common", "artifact_digest_factory"]
-    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     , ["@", "src", "src/buildtool/crypto", "hash_function"]
     , ["@", "src", "src/buildtool/file_system", "file_root"]
     , ["@", "src", "src/buildtool/file_system", "file_system_manager"]
     , ["utils", "shell_quoting"]
+    , ["utils", "test_hash_function_type"]
     ]
   , "stage": ["test", "buildtool", "file_system"]
   }
diff --git a/test/buildtool/file_system/file_root.test.cpp b/test/buildtool/file_system/file_root.test.cpp
index 1a27dd1b..94a2a552 100644
--- a/test/buildtool/file_system/file_root.test.cpp
+++ b/test/buildtool/file_system/file_root.test.cpp
@@ -25,10 +25,10 @@
 #include "src/buildtool/common/artifact_description.hpp"
 #include "src/buildtool/common/artifact_digest.hpp"
 #include "src/buildtool/common/artifact_digest_factory.hpp"
-#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/crypto/hash_function.hpp"
 #include "src/buildtool/file_system/file_system_manager.hpp"
 #include "test/utils/container_matchers.hpp"
+#include "test/utils/hermeticity/test_hash_function_type.hpp"
 #include "test/utils/shell_quoting.hpp"
 
 namespace {
@@ -380,9 +380,7 @@ static void CheckGitRoot(HashFunction::Type hash_type,
                          bool ignore_special) noexcept;
 
 TEST_CASE("Creating artifact descriptions", "[file_root]") {
-    auto const hash_type = ProtocolTraits::Instance().IsCompatible()
-                               ? HashFunction::Type::PlainSHA256
-                               : HashFunction::Type::GitSHA1;
+    auto const hash_type = TestHashType::ReadFromEnvironment();
 
     SECTION("local root") {
         CheckLocalRoot(hash_type, /*ignore_special=*/false);
diff --git a/test/buildtool/graph_traverser/TARGETS b/test/buildtool/graph_traverser/TARGETS
index d9dd7af6..b2791561 100644
--- a/test/buildtool/graph_traverser/TARGETS
+++ b/test/buildtool/graph_traverser/TARGETS
@@ -23,6 +23,7 @@
     , ["@", "src", "src/buildtool/execution_api/common", "api_bundle"]
     , ["@", "src", "src/buildtool/storage", "storage"]
     , ["@", "src", "src/buildtool/storage", "config"]
+    , ["utils", "test_hash_function_type"]
     ]
   , "stage": ["test", "buildtool", "graph_traverser"]
   }
@@ -55,10 +56,10 @@
     , ["utils", "catch-main-remote-execution"]
     , ["utils", "test_auth_config"]
     , ["utils", "test_remote_config"]
+    , ["utils", "test_hash_function_type"]
     , ["@", "src", "src/buildtool/storage", "storage"]
     , ["@", "src", "src/buildtool/storage", "config"]
     , ["@", "src", "src/buildtool/crypto", "hash_function"]
-    , ["@", "src", "src/buildtool/common", "protocol_traits"]
     ]
   , "stage": ["test", "buildtool", "graph_traverser"]
   }
diff --git a/test/buildtool/graph_traverser/graph_traverser.test.hpp b/test/buildtool/graph_traverser/graph_traverser.test.hpp
index 666b905f..cb9cb57c 100644
--- a/test/buildtool/graph_traverser/graph_traverser.test.hpp
+++ b/test/buildtool/graph_traverser/graph_traverser.test.hpp
@@ -47,6 +47,7 @@
 #include "src/buildtool/storage/config.hpp"
 #include "src/buildtool/storage/storage.hpp"
 #include "src/utils/cpp/json.hpp"
+#include "test/utils/hermeticity/test_hash_function_type.hpp"
 
 // NOLINTNEXTLINE(google-build-namespaces)
 namespace {
@@ -128,7 +129,8 @@ class TestProject {
         CommandLineArguments clargs{gtargs};
         clargs.artifacts = entry_points;
         auto const comp_graph = root_dir_ / "graph_description_compatible";
-        if (ProtocolTraits::Instance().IsCompatible() and
+        if (not ProtocolTraits::IsNative(
+                TestHashType::ReadFromEnvironment()) and
             FileSystemManager::Exists(comp_graph)) {
             clargs.graph_description = comp_graph;
         }
diff --git a/test/buildtool/graph_traverser/graph_traverser_remote.test.cpp b/test/buildtool/graph_traverser/graph_traverser_remote.test.cpp
index bf3dfe02..a7888ac4 100644
--- a/test/buildtool/graph_traverser/graph_traverser_remote.test.cpp
+++ b/test/buildtool/graph_traverser/graph_traverser_remote.test.cpp
@@ -13,12 +13,12 @@
 // limitations under the License.
 
 #include "catch2/catch_test_macros.hpp"
-#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/crypto/hash_function.hpp"
 #include "src/buildtool/execution_api/remote/config.hpp"
 #include "src/buildtool/storage/config.hpp"
 #include "src/buildtool/storage/storage.hpp"
 #include "test/buildtool/graph_traverser/graph_traverser.test.hpp"
+#include "test/utils/hermeticity/test_hash_function_type.hpp"
 #include "test/utils/remote_execution/test_auth_config.hpp"
 #include "test/utils/remote_execution/test_remote_config.hpp"
 
@@ -35,9 +35,7 @@
 
     StorageConfig::Builder builder;
     auto config = builder.SetBuildRoot(cache_dir)
-                      .SetHashType(ProtocolTraits::Instance().IsCompatible()
-                                       ? HashFunction::Type::PlainSHA256
-                                       : HashFunction::Type::GitSHA1)
+                      .SetHashType(TestHashType::ReadFromEnvironment())
                       .SetRemoteExecutionArgs(remote_config.remote_address,
                                               remote_config.platform_properties,
                                               remote_config.dispatch)
diff --git a/test/buildtool/storage/large_object_cas.test.cpp b/test/buildtool/storage/large_object_cas.test.cpp
index cbc92038..e0e3c816 100644
--- a/test/buildtool/storage/large_object_cas.test.cpp
+++ b/test/buildtool/storage/large_object_cas.test.cpp
@@ -405,7 +405,8 @@ static void TestExternal(StorageConfig const& storage_config,
             REQUIRE(FileSystemManager::IsFile(path));
         }
 
-        if (kIsTree and not ProtocolTraits::Instance().IsCompatible()) {
+        if (kIsTree and ProtocolTraits::IsTreeAllowed(
+                            storage_config.hash_function.GetType())) {
             // Tree invariants check is omitted in compatible mode.
             SECTION("Tree invariants check fails") {
                 // Check splice fails due to the tree invariants check.
@@ -606,7 +607,8 @@ TEST_CASE("LargeObjectCAS: uplink nested large objects", "[storage]") {
 
     // However, in native mode they might be reconstructed on request because
     // their entries are in the latest generation:
-    if (not ProtocolTraits::Instance().IsCompatible()) {
+    if (ProtocolTraits::IsNative(
+            storage_config.Get().hash_function.GetType())) {
         auto split_nested_tree_2 = latest.CAS().SplitTree(*nested_tree_digest);
         REQUIRE(split_nested_tree_2);
 
@@ -720,10 +722,10 @@ auto Tree::StoreRaw(LocalCAS<kDefaultDoGlobalUplink> const& cas,
         return cas.StoreBlob(content);
     };
 
-    return ProtocolTraits::Instance().IsCompatible()
-               ? BazelMsgFactory::CreateDirectoryDigestFromLocalTree(
+    return ProtocolTraits::IsNative(cas.GetHashFunction().GetType())
+               ? BazelMsgFactory::CreateGitTreeDigestFromLocalTree(
                      directory, store_blob, store_tree, store_symlink)
-               : BazelMsgFactory::CreateGitTreeDigestFromLocalTree(
+               : BazelMsgFactory::CreateDirectoryDigestFromLocalTree(
                      directory, store_blob, store_tree, store_symlink);
 }
 }  // namespace LargeTestUtils