Unit test some worker protocol serializers

Continue with the characterization testing idioms begun in
c70484454f, but this time for unit tests.

Co-authored-by: Andreas Rammhold <andreas@rammhold.de>

src/libstore/tests/worker-protocol.cc

@@ -0,0 +1,139 @@
+#include <regex>
+
+#include <nlohmann/json.hpp>
+#include <gtest/gtest.h>
+
+#include "worker-protocol.hh"
+#include "worker-protocol-impl.hh"
+#include "derived-path.hh"
+#include "tests/libstore.hh"
+
+namespace nix {
+
+class WorkerProtoTest : public LibStoreTest
+{
+public:
+    Path unitTestData = getEnv("_NIX_TEST_UNIT_DATA").value() + "/libstore/worker-protocol";
+
+    bool testAccept() {
+        return getEnv("_NIX_TEST_ACCEPT") == "1";
+    }
+
+    Path goldenMaster(std::string_view testStem) {
+        return unitTestData + "/" + testStem + ".bin";
+    }
+
+    /**
+     * Golden test for `T` reading
+     */
+    template<typename T>
+    void readTest(PathView testStem, T value)
+    {
+        if (testAccept())
+        {
+            GTEST_SKIP() << "Cannot read golden master because another test is also updating it";
+        }
+        else
+        {
+            auto expected = readFile(goldenMaster(testStem));
+
+            T got = ({
+                StringSource from { expected };
+                WorkerProto::Serialise<T>::read(
+                    *store,
+                    WorkerProto::ReadConn { .from = from });
+            });
+
+            ASSERT_EQ(got, value);
+        }
+    }
+
+    /**
+     * Golden test for `T` write
+     */
+    template<typename T>
+    void writeTest(PathView testStem, const T & value)
+    {
+        auto file = goldenMaster(testStem);
+
+        StringSink to;
+        WorkerProto::write(
+            *store,
+            WorkerProto::WriteConn { .to = to },
+            value);
+
+        if (testAccept())
+        {
+            createDirs(dirOf(file));
+            writeFile(file, to.s);
+            GTEST_SKIP() << "Updating golden master";
+        }
+        else
+        {
+            auto expected = readFile(file);
+            ASSERT_EQ(to.s, expected);
+        }
+    }
+};
+
+#define CHARACTERIZATION_TEST(NAME, STEM, VALUE)  \
+    TEST_F(WorkerProtoTest, NAME ## _read) {   \
+        readTest(STEM, VALUE);                 \
+    }                                          \
+    TEST_F(WorkerProtoTest, NAME ## _write) {  \
+        writeTest(STEM, VALUE);                \
+    }
+
+CHARACTERIZATION_TEST(
+    string,
+    "string",
+    (std::tuple<std::string, std::string, std::string, std::string, std::string> {
+        "",
+        "hi",
+        "white rabbit",
+        "大白兔",
+        "oh no \0\0\0 what was that!",
+    }))
+
+CHARACTERIZATION_TEST(
+    storePath,
+    "store-path",
+    (std::tuple<StorePath, StorePath> {
+        StorePath { "g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-foo" },
+        StorePath { "g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-foo-bar" },
+    }))
+
+CHARACTERIZATION_TEST(
+    contentAddress,
+    "content-address",
+    (std::tuple<ContentAddress, ContentAddress, ContentAddress> {
+        ContentAddress {
+            .method = TextIngestionMethod {},
+            .hash = hashString(HashType::htSHA256, "Derive(...)"),
+        },
+        ContentAddress {
+            .method = FileIngestionMethod::Flat,
+            .hash = hashString(HashType::htSHA1, "blob blob..."),
+        },
+        ContentAddress {
+            .method = FileIngestionMethod::Recursive,
+            .hash = hashString(HashType::htSHA256, "(...)"),
+        },
+    }))
+
+CHARACTERIZATION_TEST(
+    derivedPath,
+    "derived-path",
+    (std::tuple<DerivedPath, DerivedPath> {
+        DerivedPath::Opaque {
+            .path = StorePath { "g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-foo" },
+        },
+        DerivedPath::Built {
+            .drvPath = makeConstantStorePathRef(StorePath {
+                "g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-bar.drv",
+            }),
+            .outputs = OutputsSpec::Names { "x", "y" },
+        },
+    }))
+
+}