Move tests to separate directories, and document

Today, with the tests inside a `tests` intermingled with the
corresponding library's source code, we have a few problems:

- We have to be careful that wildcards don't end up with tests being
  built as part of Nix proper, or test headers being installed as part
  of Nix proper.

- Tests in libraries but not executables is not right:

  - It means each executable runs the previous unit tests again, because
    it needs the libraries.

  - It doesn't work right on Windows, which doesn't want you to load a
    DLL just for the side global variable . It could be made to work
    with the dlopen equivalent, but that's gross!

This reorg solves these problems.

There is a remaining problem which is that sibbling headers (like
`hash.hh` the test header vs `hash.hh` the main `libnixutil` header) end
up shadowing each other. This PR doesn't solve that. That is left as
future work for a future PR.

Co-authored-by: Valentin Gagarin <valentin.gagarin@tweag.io>

(cherry picked from commit 91b6833686a6a6d9eac7f3f66393ec89ef1d3b57)
(cherry picked from commit a61e42adb528b3d40ce43e07c79368d779a8b624)

61 files changed, 386 insertions, 293 deletions

diff --git a/.gitignore b/.gitignore
index 2d3314015..1e1361f5a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -41,14 +41,14 @@ perl/Makefile.config
 /src/libexpr/parser-tab.hh
 /src/libexpr/parser-tab.output
 /src/libexpr/nix.tbl
-/src/libexpr/tests/libnixexpr-tests
+/tests/unit/libexpr/libnixexpr-tests
 
 # /src/libstore/
 *.gen.*
-/src/libstore/tests/libnixstore-tests
+/tests/unit/libstore/libnixstore-tests
 
 # /src/libutil/
-/src/libutil/tests/libnixutil-tests
+/tests/unit/libutil/libnixutil-tests
 
 /src/nix/nix
 
diff --git a/Makefile b/Makefile
index c0b27e904..41c0ab68a 100644
--- a/Makefile
+++ b/Makefile
@@ -23,9 +23,12 @@ makefiles = \
 
 ifeq ($(tests), yes)
 makefiles += \
-  src/libutil/tests/local.mk \
-  src/libstore/tests/local.mk \
-  src/libexpr/tests/local.mk \
+  tests/unit/libutil/local.mk \
+  tests/unit/libutil-support/local.mk \
+  tests/unit/libstore/local.mk \
+  tests/unit/libstore-support/local.mk \
+  tests/unit/libexpr/local.mk \
+  tests/unit/libexpr-support/local.mk \
   tests/functional/local.mk \
   tests/functional/ca/local.mk \
   tests/functional/dyn-drv/local.mk \
diff --git a/doc/internal-api/doxygen.cfg.in b/doc/internal-api/doxygen.cfg.in
index 8f526536d..a339662e3 100644
--- a/doc/internal-api/doxygen.cfg.in
+++ b/doc/internal-api/doxygen.cfg.in
@@ -39,17 +39,21 @@ INPUT                  = \
   src/libcmd \
   src/libexpr \
   src/libexpr/flake \
-  src/libexpr/tests \
-  src/libexpr/tests/value \
+  tests/unit/libexpr \
+  tests/unit/libexpr/value \
+  tests/unit/libexpr/test \
+  tests/unit/libexpr/test/value \
   src/libexpr/value \
   src/libfetchers \
   src/libmain \
   src/libstore \
   src/libstore/build \
   src/libstore/builtins \
-  src/libstore/tests \
+  tests/unit/libstore \
+  tests/unit/libstore/test \
   src/libutil \
-  src/libutil/tests \
+  tests/unit/libutil \
+  tests/unit/libutil/test \
   src/nix \
   src/nix-env \
   src/nix-store
diff --git a/doc/manual/src/contributing/testing.md b/doc/manual/src/contributing/testing.md
index ccd90088e..1b15d12b1 100644
--- a/doc/manual/src/contributing/testing.md
+++ b/doc/manual/src/contributing/testing.md
@@ -3,13 +3,25 @@
 ## Unit-tests
 
 The unit-tests for each Nix library (`libexpr`, `libstore`, etc..) are defined
-under `src/{library_name}/tests` using the
+under `tests/unit/{library_name}/tests` using the
 [googletest](https://google.github.io/googletest/) and
 [rapidcheck](https://github.com/emil-e/rapidcheck) frameworks.
 
 You can run the whole testsuite with `make check`, or the tests for a specific component with `make libfoo-tests_RUN`.
 Finer-grained filtering is also possible using the [--gtest_filter](https://google.github.io/googletest/advanced.html#running-a-subset-of-the-tests) command-line option, or the `GTEST_FILTER` environment variable.
 
+### Unit test support libraries
+
+There are headers and code which are not just used to test the library in question, but also downstream libraries.
+For example, we do [property testing] with the [rapidcheck] library.
+This requires writing `Arbitrary` "instances", which are used to describe how to generate values of a given type for the sake of running property tests.
+Because types contain other types, `Arbitrary` "instances" for some type are not just useful for testing that type, but also any other type that contains it.
+Downstream types frequently contain upstream types, so it is very important that we share arbitrary instances so that downstream libraries' property tests can also use them.
+
+It is important that these testing libraries don't contain any actual tests themselves.
+On some platforms they would be run as part of every test executable that uses them, which is redundant.
+On other platforms they wouldn't be run at all.
+
 ## Functional tests
 
 The functional tests reside under the `tests/functional` directory and are listed in `tests/functional/local.mk`.
diff --git a/flake.nix b/flake.nix
index beedb000f..230bb6031 100644
--- a/flake.nix
+++ b/flake.nix
@@ -73,6 +73,7 @@
           ./precompiled-headers.h
           ./src
           ./tests/functional
+          ./tests/unit
           ./COPYING
           ./scripts/local.mk
           (fileset.fileFilter (f: lib.strings.hasPrefix "nix-profile" f.name) ./scripts)
diff --git a/src/libexpr/tests/local.mk b/src/libexpr/tests/local.mk
deleted file mode 100644
index c56848a14..000000000
--- a/src/libexpr/tests/local.mk
+++ /dev/null
@@ -1,19 +0,0 @@
-check: libexpr-tests_RUN
-
-programs += libexpr-tests
-
-libexpr-tests_NAME := libnixexpr-tests
-
-libexpr-tests_DIR := $(d)
-
-libexpr-tests_INSTALL_DIR :=
-
-libexpr-tests_SOURCES := \
-    $(wildcard $(d)/*.cc) \
-    $(wildcard $(d)/value/*.cc)
-
-libexpr-tests_CXXFLAGS += -I src/libexpr -I src/libutil -I src/libstore -I src/libexpr/tests -I src/libfetchers
-
-libexpr-tests_LIBS = libstore-tests libutils-tests libexpr libutil libstore libfetchers
-
-libexpr-tests_LDFLAGS := -lrapidcheck $(GTEST_LIBS) -lgmock
diff --git a/src/libstore/tests/local.mk b/src/libstore/tests/local.mk
deleted file mode 100644
index 03becc7d1..000000000
--- a/src/libstore/tests/local.mk
+++ /dev/null
@@ -1,29 +0,0 @@
-check: libstore-tests-exe_RUN
-
-programs += libstore-tests-exe
-
-libstore-tests-exe_NAME = libnixstore-tests
-
-libstore-tests-exe_DIR := $(d)
-
-libstore-tests-exe_INSTALL_DIR :=
-
-libstore-tests-exe_LIBS = libstore-tests
-
-libstore-tests-exe_LDFLAGS := $(GTEST_LIBS)
-
-libraries += libstore-tests
-
-libstore-tests_NAME = libnixstore-tests
-
-libstore-tests_DIR := $(d)
-
-libstore-tests_INSTALL_DIR :=
-
-libstore-tests_SOURCES := $(wildcard $(d)/*.cc)
-
-libstore-tests_CXXFLAGS += -I src/libstore -I src/libutil
-
-libstore-tests_LIBS = libutil-tests libstore libutil
-
-libstore-tests_LDFLAGS := -lrapidcheck $(GTEST_LIBS)
diff --git a/src/libutil/tests/local.mk b/src/libutil/tests/local.mk
deleted file mode 100644
index 167915439..000000000
--- a/src/libutil/tests/local.mk
+++ /dev/null
@@ -1,29 +0,0 @@
-check: libutil-tests_RUN
-
-programs += libutil-tests
-
-libutil-tests-exe_NAME = libnixutil-tests
-
-libutil-tests-exe_DIR := $(d)
-
-libutil-tests-exe_INSTALL_DIR :=
-
-libutil-tests-exe_LIBS = libutil-tests
-
-libutil-tests-exe_LDFLAGS := $(GTEST_LIBS)
-
-libraries += libutil-tests
-
-libutil-tests_NAME = libnixutil-tests
-
-libutil-tests_DIR := $(d)
-
-libutil-tests_INSTALL_DIR :=
-
-libutil-tests_SOURCES := $(wildcard $(d)/*.cc)
-
-libutil-tests_CXXFLAGS += -I src/libutil
-
-libutil-tests_LIBS = libutil
-
-libutil-tests_LDFLAGS := -lrapidcheck $(GTEST_LIBS)
diff --git a/tests/unit/libexpr-support/local.mk b/tests/unit/libexpr-support/local.mk
new file mode 100644
index 000000000..6b3ad64ee
--- /dev/null
+++ b/tests/unit/libexpr-support/local.mk
@@ -0,0 +1,19 @@
+libraries += libexpr-test-support
+
+libexpr-test-support_NAME = libnixexpr-test-support
+
+libexpr-test-support_DIR := $(d)
+
+libexpr-test-support_INSTALL_DIR :=
+
+libexpr-test-support_SOURCES := \
+    $(wildcard $(d)/tests/*.cc) \
+    $(wildcard $(d)/tests/value/*.cc)
+
+libexpr-test-support_CXXFLAGS += $(libexpr-tests_EXTRA_INCLUDES)
+
+libexpr-test-support_LIBS = \
+    libstore-test-support libutil-test-support \
+    libexpr libstore libutil
+
+libexpr-test-support_LDFLAGS := -lrapidcheck
diff --git a/src/libexpr/tests/libexpr.hh b/tests/unit/libexpr-support/tests/libexpr.hh
index b8e65aafe..b8e65aafe 100644
--- a/src/libexpr/tests/libexpr.hh
+++ b/tests/unit/libexpr-support/tests/libexpr.hh
diff --git a/tests/unit/libexpr-support/tests/value/context.cc b/tests/unit/libexpr-support/tests/value/context.cc
new file mode 100644
index 000000000..8658bdaef
--- /dev/null
+++ b/tests/unit/libexpr-support/tests/value/context.cc
@@ -0,0 +1,30 @@
+#include <rapidcheck.h>
+
+#include "tests/path.hh"
+#include "tests/value/context.hh"
+
+namespace rc {
+using namespace nix;
+
+Gen<NixStringContextElem::DrvDeep> Arbitrary<NixStringContextElem::DrvDeep>::arbitrary()
+{
+    return gen::just(NixStringContextElem::DrvDeep {
+        .drvPath = *gen::arbitrary<StorePath>(),
+    });
+}
+
+Gen<NixStringContextElem> Arbitrary<NixStringContextElem>::arbitrary()
+{
+    switch (*gen::inRange<uint8_t>(0, std::variant_size_v<NixStringContextElem::Raw>)) {
+    case 0:
+        return gen::just<NixStringContextElem>(*gen::arbitrary<NixStringContextElem::Opaque>());
+    case 1:
+        return gen::just<NixStringContextElem>(*gen::arbitrary<NixStringContextElem::DrvDeep>());
+    case 2:
+        return gen::just<NixStringContextElem>(*gen::arbitrary<NixStringContextElem::Built>());
+    default:
+        assert(false);
+    }
+}
+
+}
diff --git a/src/libexpr/tests/value/context.hh b/tests/unit/libexpr-support/tests/value/context.hh
index c0bc97ba3..8c68c78bb 100644
--- a/src/libexpr/tests/value/context.hh
+++ b/tests/unit/libexpr-support/tests/value/context.hh
@@ -3,7 +3,7 @@
 
 #include <rapidcheck/gen/Arbitrary.h>
 
-#include <value/context.hh>
+#include "value/context.hh"
 
 namespace rc {
 using namespace nix;
diff --git a/src/libexpr/tests/derived-path.cc b/tests/unit/libexpr/derived-path.cc
index d5fc6f201..d5fc6f201 100644
--- a/src/libexpr/tests/derived-path.cc
+++ b/tests/unit/libexpr/derived-path.cc
diff --git a/src/libexpr/tests/error_traces.cc b/tests/unit/libexpr/error_traces.cc
index 285651256..285651256 100644
--- a/src/libexpr/tests/error_traces.cc
+++ b/tests/unit/libexpr/error_traces.cc
diff --git a/src/libexpr/tests/flakeref.cc b/tests/unit/libexpr/flakeref.cc
index 2b7809b93..2b7809b93 100644
--- a/src/libexpr/tests/flakeref.cc
+++ b/tests/unit/libexpr/flakeref.cc
diff --git a/src/libexpr/tests/json.cc b/tests/unit/libexpr/json.cc
index 7586bdd9b..7586bdd9b 100644
--- a/src/libexpr/tests/json.cc
+++ b/tests/unit/libexpr/json.cc
diff --git a/tests/unit/libexpr/local.mk b/tests/unit/libexpr/local.mk
new file mode 100644
index 000000000..068dd7a17
--- /dev/null
+++ b/tests/unit/libexpr/local.mk
@@ -0,0 +1,32 @@
+check: libexpr-tests_RUN
+
+programs += libexpr-tests
+
+libexpr-tests_NAME := libnixexpr-tests
+
+libexpr-tests_ENV := _NIX_TEST_UNIT_DATA=$(d)/data
+
+libexpr-tests_DIR := $(d)
+
+libexpr-tests_INSTALL_DIR :=
+
+libexpr-tests_SOURCES := \
+    $(wildcard $(d)/*.cc) \
+    $(wildcard $(d)/value/*.cc)
+
+libexpr-tests_EXTRA_INCLUDES = \
+    -I tests/unit/libexpr-support \
+    -I tests/unit/libstore-support \
+    -I tests/unit/libutil-support \
+    -I src/libexpr \
+    -I src/libfetchers \
+    -I src/libstore \
+    -I src/libutil
+
+libexpr-tests_CXXFLAGS += $(libexpr-tests_EXTRA_INCLUDES)
+
+libexpr-tests_LIBS = \
+    libexpr-test-support libstore-test-support libutils-test-support \
+    libexpr libfetchers libstore libutil
+
+libexpr-tests_LDFLAGS := -lrapidcheck $(GTEST_LIBS) -lgmock
diff --git a/src/libexpr/tests/primops.cc b/tests/unit/libexpr/primops.cc
index ce3b5d11f..ce3b5d11f 100644
--- a/src/libexpr/tests/primops.cc
+++ b/tests/unit/libexpr/primops.cc
diff --git a/src/libexpr/tests/search-path.cc b/tests/unit/libexpr/search-path.cc
index dbe7ab95f..dbe7ab95f 100644
--- a/src/libexpr/tests/search-path.cc
+++ b/tests/unit/libexpr/search-path.cc
diff --git a/src/libexpr/tests/trivial.cc b/tests/unit/libexpr/trivial.cc
index 171727ac7..171727ac7 100644
--- a/src/libexpr/tests/trivial.cc
+++ b/tests/unit/libexpr/trivial.cc
diff --git a/src/libexpr/tests/value/context.cc b/tests/unit/libexpr/value/context.cc
index 92d4889ab..761286dbd 100644
--- a/src/libexpr/tests/value/context.cc
+++ b/tests/unit/libexpr/value/context.cc
@@ -117,36 +117,6 @@ TEST(NixStringContextElemTest, built_built_xp) {
         NixStringContextElem::parse("!foo!bar!g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-x.drv"),        MissingExperimentalFeature);
 }
 
-}
-
-namespace rc {
-using namespace nix;
-
-Gen<NixStringContextElem::DrvDeep> Arbitrary<NixStringContextElem::DrvDeep>::arbitrary()
-{
-    return gen::just(NixStringContextElem::DrvDeep {
-        .drvPath = *gen::arbitrary<StorePath>(),
-    });
-}
-
-Gen<NixStringContextElem> Arbitrary<NixStringContextElem>::arbitrary()
-{
-    switch (*gen::inRange<uint8_t>(0, std::variant_size_v<NixStringContextElem::Raw>)) {
-    case 0:
-        return gen::just<NixStringContextElem>(*gen::arbitrary<NixStringContextElem::Opaque>());
-    case 1:
-        return gen::just<NixStringContextElem>(*gen::arbitrary<NixStringContextElem::DrvDeep>());
-    case 2:
-        return gen::just<NixStringContextElem>(*gen::arbitrary<NixStringContextElem::Built>());
-    default:
-        assert(false);
-    }
-}
-
-}
-
-namespace nix {
-
 #ifndef COVERAGE
 
 RC_GTEST_PROP(
diff --git a/src/libexpr/tests/value/print.cc b/tests/unit/libexpr/value/print.cc
index 5e96e12ec..5e96e12ec 100644
--- a/src/libexpr/tests/value/print.cc
+++ b/tests/unit/libexpr/value/print.cc
diff --git a/tests/unit/libstore-support/local.mk b/tests/unit/libstore-support/local.mk
new file mode 100644
index 000000000..2738278d8
--- /dev/null
+++ b/tests/unit/libstore-support/local.mk
@@ -0,0 +1,17 @@
+libraries += libstore-test-support
+
+libstore-test-support_NAME = libnixstore-test-support
+
+libstore-test-support_DIR := $(d)
+
+libstore-test-support_INSTALL_DIR :=
+
+libstore-test-support_SOURCES := $(wildcard $(d)/tests/*.cc)
+
+libstore-test-support_CXXFLAGS += $(libstore-tests_EXTRA_INCLUDES)
+
+libstore-test-support_LIBS = \
+    libutil-test-support \
+    libstore libutil
+
+libstore-test-support_LDFLAGS := -lrapidcheck
diff --git a/tests/unit/libstore-support/tests/derived-path.cc b/tests/unit/libstore-support/tests/derived-path.cc
new file mode 100644
index 000000000..091706dba
--- /dev/null
+++ b/tests/unit/libstore-support/tests/derived-path.cc
@@ -0,0 +1,57 @@
+#include <regex>
+
+#include <rapidcheck.h>
+
+#include "tests/derived-path.hh"
+
+namespace rc {
+using namespace nix;
+
+Gen<DerivedPath::Opaque> Arbitrary<DerivedPath::Opaque>::arbitrary()
+{
+    return gen::just(DerivedPath::Opaque {
+        .path = *gen::arbitrary<StorePath>(),
+    });
+}
+
+Gen<SingleDerivedPath::Built> Arbitrary<SingleDerivedPath::Built>::arbitrary()
+{
+    return gen::just(SingleDerivedPath::Built {
+        .drvPath = make_ref<SingleDerivedPath>(*gen::arbitrary<SingleDerivedPath>()),
+        .output = (*gen::arbitrary<StorePathName>()).name,
+    });
+}
+
+Gen<DerivedPath::Built> Arbitrary<DerivedPath::Built>::arbitrary()
+{
+    return gen::just(DerivedPath::Built {
+        .drvPath = make_ref<SingleDerivedPath>(*gen::arbitrary<SingleDerivedPath>()),
+        .outputs = *gen::arbitrary<OutputsSpec>(),
+    });
+}
+
+Gen<SingleDerivedPath> Arbitrary<SingleDerivedPath>::arbitrary()
+{
+    switch (*gen::inRange<uint8_t>(0, std::variant_size_v<SingleDerivedPath::Raw>)) {
+    case 0:
+        return gen::just<SingleDerivedPath>(*gen::arbitrary<SingleDerivedPath::Opaque>());
+    case 1:
+        return gen::just<SingleDerivedPath>(*gen::arbitrary<SingleDerivedPath::Built>());
+    default:
+        assert(false);
+    }
+}
+
+Gen<DerivedPath> Arbitrary<DerivedPath>::arbitrary()
+{
+    switch (*gen::inRange<uint8_t>(0, std::variant_size_v<DerivedPath::Raw>)) {
+    case 0:
+        return gen::just<DerivedPath>(*gen::arbitrary<DerivedPath::Opaque>());
+    case 1:
+        return gen::just<DerivedPath>(*gen::arbitrary<DerivedPath::Built>());
+    default:
+        assert(false);
+    }
+}
+
+}
diff --git a/src/libstore/tests/derived-path.hh b/tests/unit/libstore-support/tests/derived-path.hh
index 98d61f228..98d61f228 100644
--- a/src/libstore/tests/derived-path.hh
+++ b/tests/unit/libstore-support/tests/derived-path.hh
diff --git a/src/libstore/tests/libstore.hh b/tests/unit/libstore-support/tests/libstore.hh
index ef93457b5..ef93457b5 100644
--- a/src/libstore/tests/libstore.hh
+++ b/tests/unit/libstore-support/tests/libstore.hh
diff --git a/tests/unit/libstore-support/tests/outputs-spec.cc b/tests/unit/libstore-support/tests/outputs-spec.cc
new file mode 100644
index 000000000..e9d602203
--- /dev/null
+++ b/tests/unit/libstore-support/tests/outputs-spec.cc
@@ -0,0 +1,24 @@
+#include "tests/outputs-spec.hh"
+
+#include <rapidcheck.h>
+
+namespace rc {
+using namespace nix;
+
+Gen<OutputsSpec> Arbitrary<OutputsSpec>::arbitrary()
+{
+    switch (*gen::inRange<uint8_t>(0, std::variant_size_v<OutputsSpec::Raw>)) {
+    case 0:
+        return gen::just((OutputsSpec) OutputsSpec::All { });
+    case 1:
+        return gen::just((OutputsSpec) OutputsSpec::Names {
+            *gen::nonEmpty(gen::container<StringSet>(gen::map(
+                gen::arbitrary<StorePathName>(),
+                [](StorePathName n) { return n.name; }))),
+        });
+    default:
+        assert(false);
+    }
+}
+
+}
diff --git a/src/libstore/tests/outputs-spec.hh b/tests/unit/libstore-support/tests/outputs-spec.hh
index ded331b33..f5bf9042d 100644
--- a/src/libstore/tests/outputs-spec.hh
+++ b/tests/unit/libstore-support/tests/outputs-spec.hh
@@ -5,7 +5,7 @@
 
 #include <outputs-spec.hh>
 
-#include <tests/path.hh>
+#include "tests/path.hh"
 
 namespace rc {
 using namespace nix;
diff --git a/tests/unit/libstore-support/tests/path.cc b/tests/unit/libstore-support/tests/path.cc
new file mode 100644
index 000000000..e5f169e94
--- /dev/null
+++ b/tests/unit/libstore-support/tests/path.cc
@@ -0,0 +1,82 @@
+#include <regex>
+
+#include <rapidcheck.h>
+
+#include "path-regex.hh"
+#include "store-api.hh"
+
+#include "tests/hash.hh"
+#include "tests/path.hh"
+
+namespace nix {
+
+void showValue(const StorePath & p, std::ostream & os)
+{
+    os << p.to_string();
+}
+
+}
+
+namespace rc {
+using namespace nix;
+
+Gen<StorePathName> Arbitrary<StorePathName>::arbitrary()
+{
+    auto len = *gen::inRange<size_t>(
+        1,
+        StorePath::MaxPathLen - StorePath::HashLen);
+
+    std::string pre;
+    pre.reserve(len);
+
+    for (size_t c = 0; c < len; ++c) {
+        switch (auto i = *gen::inRange<uint8_t>(0, 10 + 2 * 26 + 6)) {
+            case 0 ... 9:
+                pre += '0' + i;
+            case 10 ... 35:
+                pre += 'A' + (i - 10);
+                break;
+            case 36 ... 61:
+                pre += 'a' + (i - 36);
+                break;
+            case 62:
+                pre += '+';
+                break;
+            case 63:
+                pre += '-';
+                break;
+            case 64:
+                // names aren't permitted to start with a period,
+                // so just fall through to the next case here
+                if (c != 0) {
+                    pre += '.';
+                    break;
+                }
+            case 65:
+                pre += '_';
+                break;
+            case 66:
+                pre += '?';
+                break;
+            case 67:
+                pre += '=';
+                break;
+            default:
+                assert(false);
+        }
+    }
+
+    return gen::just(StorePathName {
+        .name = std::move(pre),
+    });
+}
+
+Gen<StorePath> Arbitrary<StorePath>::arbitrary()
+{
+    return gen::just(StorePath {
+        *gen::arbitrary<Hash>(),
+        (*gen::arbitrary<StorePathName>()).name,
+    });
+}
+
+} // namespace rc
diff --git a/src/libstore/tests/path.hh b/tests/unit/libstore-support/tests/path.hh
index 21cb62310..4751b3373 100644
--- a/src/libstore/tests/path.hh
+++ b/tests/unit/libstore-support/tests/path.hh
@@ -11,6 +11,9 @@ struct StorePathName {
     std::string name;
 };
 
+// For rapidcheck
+void showValue(const StorePath & p, std::ostream & os);
+
 }
 
 namespace rc {
diff --git a/src/libstore/tests/derivation.cc b/tests/unit/libstore/derivation.cc
index c360c9707..c360c9707 100644
--- a/src/libstore/tests/derivation.cc
+++ b/tests/unit/libstore/derivation.cc
diff --git a/src/libstore/tests/derived-path.cc b/tests/unit/libstore/derived-path.cc
index 3fa3c0801..c62d79a78 100644
--- a/src/libstore/tests/derived-path.cc
+++ b/tests/unit/libstore/derived-path.cc
@@ -1,64 +1,11 @@
 #include <regex>
 
-#include <nlohmann/json.hpp>
 #include <gtest/gtest.h>
 #include <rapidcheck/gtest.h>
 
 #include "tests/derived-path.hh"
 #include "tests/libstore.hh"
 
-namespace rc {
-using namespace nix;
-
-Gen<DerivedPath::Opaque> Arbitrary<DerivedPath::Opaque>::arbitrary()
-{
-    return gen::just(DerivedPath::Opaque {
-        .path = *gen::arbitrary<StorePath>(),
-    });
-}
-
-Gen<SingleDerivedPath::Built> Arbitrary<SingleDerivedPath::Built>::arbitrary()
-{
-    return gen::just(SingleDerivedPath::Built {
-        .drvPath = make_ref<SingleDerivedPath>(*gen::arbitrary<SingleDerivedPath>()),
-        .output = (*gen::arbitrary<StorePathName>()).name,
-    });
-}
-
-Gen<DerivedPath::Built> Arbitrary<DerivedPath::Built>::arbitrary()
-{
-    return gen::just(DerivedPath::Built {
-        .drvPath = make_ref<SingleDerivedPath>(*gen::arbitrary<SingleDerivedPath>()),
-        .outputs = *gen::arbitrary<OutputsSpec>(),
-    });
-}
-
-Gen<SingleDerivedPath> Arbitrary<SingleDerivedPath>::arbitrary()
-{
-    switch (*gen::inRange<uint8_t>(0, std::variant_size_v<SingleDerivedPath::Raw>)) {
-    case 0:
-        return gen::just<SingleDerivedPath>(*gen::arbitrary<SingleDerivedPath::Opaque>());
-    case 1:
-        return gen::just<SingleDerivedPath>(*gen::arbitrary<SingleDerivedPath::Built>());
-    default:
-        assert(false);
-    }
-}
-
-Gen<DerivedPath> Arbitrary<DerivedPath>::arbitrary()
-{
-    switch (*gen::inRange<uint8_t>(0, std::variant_size_v<DerivedPath::Raw>)) {
-    case 0:
-        return gen::just<DerivedPath>(*gen::arbitrary<DerivedPath::Opaque>());
-    case 1:
-        return gen::just<DerivedPath>(*gen::arbitrary<DerivedPath::Built>());
-    default:
-        assert(false);
-    }
-}
-
-}
-
 namespace nix {
 
 class DerivedPathTest : public LibStoreTest
diff --git a/src/libstore/tests/downstream-placeholder.cc b/tests/unit/libstore/downstream-placeholder.cc
index fd29530ac..fd29530ac 100644
--- a/src/libstore/tests/downstream-placeholder.cc
+++ b/tests/unit/libstore/downstream-placeholder.cc
diff --git a/tests/unit/libstore/local.mk b/tests/unit/libstore/local.mk
new file mode 100644
index 000000000..fb7385ec1
--- /dev/null
+++ b/tests/unit/libstore/local.mk
@@ -0,0 +1,27 @@
+check: libstore-tests_RUN
+
+programs += libstore-tests
+
+libstore-tests_NAME = libnixstore-tests
+
+libstore-tests_ENV := _NIX_TEST_UNIT_DATA=$(d)/data
+
+libstore-tests_DIR := $(d)
+
+libstore-tests_INSTALL_DIR :=
+
+libstore-tests_SOURCES := $(wildcard $(d)/*.cc)
+
+libstore-tests_EXTRA_INCLUDES = \
+    -I tests/unit/libstore-support \
+    -I tests/unit/libutil-support \
+    -I src/libstore \
+    -I src/libutil
+
+libstore-tests_CXXFLAGS += $(libstore-tests_EXTRA_INCLUDES)
+
+libstore-tests_LIBS = \
+    libstore-test-support libutil-test-support \
+    libstore libutil
+
+libstore-tests_LDFLAGS := -lrapidcheck $(GTEST_LIBS)
diff --git a/src/libstore/tests/machines.cc b/tests/unit/libstore/machines.cc
index f51052b14..72b2c3ac6 100644
--- a/src/libstore/tests/machines.cc
+++ b/tests/unit/libstore/machines.cc
@@ -137,7 +137,7 @@ TEST(machines, getMachinesWithIncorrectFormat) {
 }
 
 TEST(machines, getMachinesWithCorrectFileReference) {
-    auto path = absPath("src/libstore/tests/test-data/machines.valid");
+    auto path = absPath("tests/unit/libstore/test-data/machines.valid");
     ASSERT_TRUE(pathExists(path));
 
     settings.builders = std::string("@") + path;
@@ -164,6 +164,6 @@ TEST(machines, getMachinesWithIncorrectFileReference) {
 }
 
 TEST(machines, getMachinesWithCorrectFileReferenceToIncorrectFile) {
-    settings.builders = std::string("@") + absPath("src/libstore/tests/test-data/machines.bad_format");
+    settings.builders = std::string("@") + absPath("tests/unit/libstore/test-data/machines.bad_format");
     EXPECT_THROW(getMachines(), FormatError);
 }
diff --git a/src/libstore/tests/nar-info-disk-cache.cc b/tests/unit/libstore/nar-info-disk-cache.cc
index b4bdb8329..b4bdb8329 100644
--- a/src/libstore/tests/nar-info-disk-cache.cc
+++ b/tests/unit/libstore/nar-info-disk-cache.cc
diff --git a/src/libstore/tests/outputs-spec.cc b/tests/unit/libstore/outputs-spec.cc
index 952945185..456196be1 100644
--- a/src/libstore/tests/outputs-spec.cc
+++ b/tests/unit/libstore/outputs-spec.cc
@@ -1,4 +1,4 @@
-#include "outputs-spec.hh"
+#include "tests/outputs-spec.hh"
 
 #include <nlohmann/json.hpp>
 #include <gtest/gtest.h>
@@ -199,31 +199,6 @@ TEST_JSON(ExtendedOutputsSpec, names, R"(["a","b"])", (ExtendedOutputsSpec::Expl
 
 #undef TEST_JSON
 
-}
-
-namespace rc {
-using namespace nix;
-
-Gen<OutputsSpec> Arbitrary<OutputsSpec>::arbitrary()
-{
-    switch (*gen::inRange<uint8_t>(0, std::variant_size_v<OutputsSpec::Raw>)) {
-    case 0:
-        return gen::just((OutputsSpec) OutputsSpec::All { });
-    case 1:
-        return gen::just((OutputsSpec) OutputsSpec::Names {
-            *gen::nonEmpty(gen::container<StringSet>(gen::map(
-                gen::arbitrary<StorePathName>(),
-                [](StorePathName n) { return n.name; }))),
-        });
-    default:
-        assert(false);
-    }
-}
-
-}
-
-namespace nix {
-
 #ifndef COVERAGE
 
 RC_GTEST_PROP(
diff --git a/src/libstore/tests/path.cc b/tests/unit/libstore/path.cc
index 5a84d646c..30631b5fd 100644
--- a/src/libstore/tests/path.cc
+++ b/tests/unit/libstore/path.cc
@@ -66,79 +66,6 @@ TEST_DO_PARSE(equals_sign, "foo=foo")
 
 #undef TEST_DO_PARSE
 
-// For rapidcheck
-void showValue(const StorePath & p, std::ostream & os) {
-    os << p.to_string();
-}
-
-}
-
-namespace rc {
-using namespace nix;
-
-Gen<StorePathName> Arbitrary<StorePathName>::arbitrary()
-{
-    auto len = *gen::inRange<size_t>(
-        1,
-        StorePath::MaxPathLen - std::string_view { HASH_PART }.size());
-
-    std::string pre;
-    pre.reserve(len);
-
-    for (size_t c = 0; c < len; ++c) {
-        switch (auto i = *gen::inRange<uint8_t>(0, 10 + 2 * 26 + 6)) {
-            case 0 ... 9:
-                pre += '0' + i;
-            case 10 ... 35:
-                pre += 'A' + (i - 10);
-                break;
-            case 36 ... 61:
-                pre += 'a' + (i - 36);
-                break;
-            case 62:
-                pre += '+';
-                break;
-            case 63:
-                pre += '-';
-                break;
-            case 64:
-                // names aren't permitted to start with a period,
-                // so just fall through to the next case here
-                if (c != 0) {
-                    pre += '.';
-                    break;
-                }
-            case 65:
-                pre += '_';
-                break;
-            case 66:
-                pre += '?';
-                break;
-            case 67:
-                pre += '=';
-                break;
-            default:
-                assert(false);
-        }
-    }
-
-    return gen::just(StorePathName {
-        .name = std::move(pre),
-    });
-}
-
-Gen<StorePath> Arbitrary<StorePath>::arbitrary()
-{
-    return gen::just(StorePath {
-        *gen::arbitrary<Hash>(),
-        (*gen::arbitrary<StorePathName>()).name,
-    });
-}
-
-} // namespace rc
-
-namespace nix {
-
 #ifndef COVERAGE
 
 RC_GTEST_FIXTURE_PROP(
diff --git a/src/libstore/tests/references.cc b/tests/unit/libstore/references.cc
index d91d1cedd..d91d1cedd 100644
--- a/src/libstore/tests/references.cc
+++ b/tests/unit/libstore/references.cc
diff --git a/src/libstore/tests/test-data/machines.bad_format b/tests/unit/libstore/test-data/machines.bad_format
index 7255a1216..7255a1216 100644
--- a/src/libstore/tests/test-data/machines.bad_format
+++ b/tests/unit/libstore/test-data/machines.bad_format
diff --git a/src/libstore/tests/test-data/machines.valid b/tests/unit/libstore/test-data/machines.valid
index 1a6c8017c..1a6c8017c 100644
--- a/src/libstore/tests/test-data/machines.valid
+++ b/tests/unit/libstore/test-data/machines.valid
diff --git a/tests/unit/libutil-support/local.mk b/tests/unit/libutil-support/local.mk
new file mode 100644
index 000000000..d085eda4e
--- /dev/null
+++ b/tests/unit/libutil-support/local.mk
@@ -0,0 +1,15 @@
+libraries += libutil-test-support
+
+libutil-test-support_NAME = libnixutil-test-support
+
+libutil-test-support_DIR := $(d)
+
+libutil-test-support_INSTALL_DIR :=
+
+libutil-test-support_SOURCES := $(wildcard $(d)/tests/*.cc)
+
+libutil-test-support_CXXFLAGS += $(libutil-tests_EXTRA_INCLUDES)
+
+libutil-test-support_LIBS = libutil
+
+libutil-test-support_LDFLAGS := -lrapidcheck
diff --git a/tests/unit/libutil-support/tests/hash.cc b/tests/unit/libutil-support/tests/hash.cc
new file mode 100644
index 000000000..577e9890e
--- /dev/null
+++ b/tests/unit/libutil-support/tests/hash.cc
@@ -0,0 +1,20 @@
+#include <regex>
+
+#include <rapidcheck.h>
+
+#include "hash.hh"
+
+#include "tests/hash.hh"
+
+namespace rc {
+using namespace nix;
+
+Gen<Hash> Arbitrary<Hash>::arbitrary()
+{
+    Hash hash(htSHA1);
+    for (size_t i = 0; i < hash.hashSize; ++i)
+        hash.hash[i] = *gen::arbitrary<uint8_t>();
+    return gen::just(hash);
+}
+
+}
diff --git a/src/libutil/tests/hash.hh b/tests/unit/libutil-support/tests/hash.hh
index 1f9fa59ae..1f9fa59ae 100644
--- a/src/libutil/tests/hash.hh
+++ b/tests/unit/libutil-support/tests/hash.hh
diff --git a/src/libutil/tests/canon-path.cc b/tests/unit/libutil/canon-path.cc
index fc94ccc3d..fc94ccc3d 100644
--- a/src/libutil/tests/canon-path.cc
+++ b/tests/unit/libutil/canon-path.cc
diff --git a/src/libutil/tests/chunked-vector.cc b/tests/unit/libutil/chunked-vector.cc
index 868d11f6f..868d11f6f 100644
--- a/src/libutil/tests/chunked-vector.cc
+++ b/tests/unit/libutil/chunked-vector.cc
diff --git a/src/libutil/tests/closure.cc b/tests/unit/libutil/closure.cc
index 7597e7807..7597e7807 100644
--- a/src/libutil/tests/closure.cc
+++ b/tests/unit/libutil/closure.cc
diff --git a/src/libutil/tests/compression.cc b/tests/unit/libutil/compression.cc
index bbbf3500f..bbbf3500f 100644
--- a/src/libutil/tests/compression.cc
+++ b/tests/unit/libutil/compression.cc
diff --git a/src/libutil/tests/config.cc b/tests/unit/libutil/config.cc
index 886e70da5..886e70da5 100644
--- a/src/libutil/tests/config.cc
+++ b/tests/unit/libutil/config.cc
diff --git a/src/libutil/tests/git.cc b/tests/unit/libutil/git.cc
index 5b5715fc2..5b5715fc2 100644
--- a/src/libutil/tests/git.cc
+++ b/tests/unit/libutil/git.cc
diff --git a/src/libutil/tests/hash.cc b/tests/unit/libutil/hash.cc
index e4e928b3b..1f40edc95 100644
--- a/src/libutil/tests/hash.cc
+++ b/tests/unit/libutil/hash.cc
@@ -1,12 +1,8 @@
 #include <regex>
 
-#include <nlohmann/json.hpp>
 #include <gtest/gtest.h>
-#include <rapidcheck/gtest.h>
 
-#include <hash.hh>
-
-#include "tests/hash.hh"
+#include "hash.hh"
 
 namespace nix {
 
@@ -68,7 +64,6 @@ namespace nix {
                 "7ea20a9eeee64b55d39a2192992a274fc1a836ba3c23a3feebbd"
                 "454d4423643ce80e2a9ac94fa54ca49f");
     }
-
     TEST(hashString, testKnownSHA512Hashes2) {
         // values taken from: https://tools.ietf.org/html/rfc4634
         auto s = "abcdefghbcdefghicdefghijdefghijkefghijklfghijklmghijklmnhijklmnoijklmnopjklmnopqklmnopqrlmnopqrsmnopqrstnopqrstu";
@@ -80,16 +75,3 @@ namespace nix {
                 "c7d329eeb6dd26545e96e55b874be909");
     }
 }
-
-namespace rc {
-using namespace nix;
-
-Gen<Hash> Arbitrary<Hash>::arbitrary()
-{
-    Hash hash(htSHA1);
-    for (size_t i = 0; i < hash.hashSize; ++i)
-        hash.hash[i] = *gen::arbitrary<uint8_t>();
-    return gen::just(hash);
-}
-
-}
diff --git a/src/libutil/tests/hilite.cc b/tests/unit/libutil/hilite.cc
index 1ff5980d5..1ff5980d5 100644
--- a/src/libutil/tests/hilite.cc
+++ b/tests/unit/libutil/hilite.cc
diff --git a/tests/unit/libutil/local.mk b/tests/unit/libutil/local.mk
new file mode 100644
index 000000000..6de96c0dc
--- /dev/null
+++ b/tests/unit/libutil/local.mk
@@ -0,0 +1,23 @@
+check: libutil-tests_RUN
+
+programs += libutil-tests
+
+libutil-tests_NAME = libnixutil-tests
+
+libutil-tests_ENV := _NIX_TEST_UNIT_DATA=$(d)/data
+
+libutil-tests_DIR := $(d)
+
+libutil-tests_INSTALL_DIR :=
+
+libutil-tests_SOURCES := $(wildcard $(d)/*.cc)
+
+libutil-tests_EXTRA_INCLUDES = \
+    -I tests/unit/libutil-support \
+    -I src/libutil
+
+libutil-tests_CXXFLAGS += $(libutil-tests_EXTRA_INCLUDES)
+
+libutil-tests_LIBS = libutil-test-support libutil
+
+libutil-tests_LDFLAGS := -lrapidcheck $(GTEST_LIBS)
diff --git a/src/libutil/tests/logging.cc b/tests/unit/libutil/logging.cc
index 2ffdc2e9b..2ffdc2e9b 100644
--- a/src/libutil/tests/logging.cc
+++ b/tests/unit/libutil/logging.cc
diff --git a/src/libutil/tests/lru-cache.cc b/tests/unit/libutil/lru-cache.cc
index 091d3d5ed..091d3d5ed 100644
--- a/src/libutil/tests/lru-cache.cc
+++ b/tests/unit/libutil/lru-cache.cc
diff --git a/src/libutil/tests/pool.cc b/tests/unit/libutil/pool.cc
index 127e42dda..127e42dda 100644
--- a/src/libutil/tests/pool.cc
+++ b/tests/unit/libutil/pool.cc
diff --git a/src/libutil/tests/references.cc b/tests/unit/libutil/references.cc
index a517d9aa1..a517d9aa1 100644
--- a/src/libutil/tests/references.cc
+++ b/tests/unit/libutil/references.cc
diff --git a/src/libutil/tests/suggestions.cc b/tests/unit/libutil/suggestions.cc
index 279994abc..279994abc 100644
--- a/src/libutil/tests/suggestions.cc
+++ b/tests/unit/libutil/suggestions.cc
diff --git a/src/libutil/tests/tests.cc b/tests/unit/libutil/tests.cc
index f3c1e8248..f3c1e8248 100644
--- a/src/libutil/tests/tests.cc
+++ b/tests/unit/libutil/tests.cc
diff --git a/src/libutil/tests/url.cc b/tests/unit/libutil/url.cc
index a908631e6..a908631e6 100644
--- a/src/libutil/tests/url.cc
+++ b/tests/unit/libutil/url.cc
diff --git a/src/libutil/tests/xml-writer.cc b/tests/unit/libutil/xml-writer.cc
index adcde25c9..adcde25c9 100644
--- a/src/libutil/tests/xml-writer.cc
+++ b/tests/unit/libutil/xml-writer.cc