[RFC PATCH 1/4] t0080: turn t-basic unit test into a helper

[Josh Steadmon <steadmon@google.com>]

While t/unit-tests/t-basic.c uses the unit-test framework added in
e137fe3b29 (unit tests: add TAP unit test framework, 2023-11-09), it is
not a true unit test in that it intentionally fails in order to exercise
various codepaths in the unit-test framework. Thus, we intentionally
exclude it when running unit tests through the various t/Makefile
targets. Instead, it is executed by t0080-unit-test-output.sh, which
verifies its output follows the TAP format expected for the various
pass, skip, or fail cases.

As such, it makes more sense for t-basic to be a helper item for
t0080-unit-test-output.sh, so let's move it to t/t0080/t-basic.c and
adjust Makefiles and .gitignores as necessary.

This has the additional benefit that test harnesses seeking to run all
unit tests can find them with a simple glob of "t/unit-tests/bin/t-*",
with no exceptions needed. This will be important in a later patch where
we add support for running the unit tests via a test-tool subcommand.

Signed-off-by: Josh Steadmon <steadmon@google.com>
---
 Makefile                          | 17 +++++++++++++----
 t/Makefile                        |  2 +-
 t/t0080-unit-test-output.sh       | 24 ++++++++++++------------
 t/t0080/.gitignore                |  1 +
 t/{unit-tests => t0080}/t-basic.c |  2 +-
 5 files changed, 28 insertions(+), 18 deletions(-)
 create mode 100644 t/t0080/.gitignore
 rename t/{unit-tests => t0080}/t-basic.c (98%)

diff --git a/Makefile b/Makefile
index 88ba7a3c51..ab32ec1101 100644
--- a/Makefile
+++ b/Makefile
@@ -683,6 +683,7 @@ TEST_OBJS =
 TEST_PROGRAMS_NEED_X =
 THIRD_PARTY_SOURCES =
 UNIT_TEST_PROGRAMS =
+UNIT_TEST_HELPERS =
 UNIT_TEST_DIR = t/unit-tests
 UNIT_TEST_BIN = $(UNIT_TEST_DIR)/bin
 
@@ -1339,10 +1340,12 @@ THIRD_PARTY_SOURCES += compat/regex/%
 THIRD_PARTY_SOURCES += sha1collisiondetection/%
 THIRD_PARTY_SOURCES += sha1dc/%
 
-UNIT_TEST_PROGRAMS += t-basic
 UNIT_TEST_PROGRAMS += t-strbuf
 UNIT_TEST_PROGS = $(patsubst %,$(UNIT_TEST_BIN)/%$X,$(UNIT_TEST_PROGRAMS))
+UNIT_TEST_HELPERS += t/t0080/t-basic
+UNIT_TEST_HELPER_PROGS = $(patsubst %,%$X,$(UNIT_TEST_HELPERS))
 UNIT_TEST_OBJS = $(patsubst %,$(UNIT_TEST_DIR)/%.o,$(UNIT_TEST_PROGRAMS))
+UNIT_TEST_OBJS += $(patsubst %,%.o,$(UNIT_TEST_HELPERS))
 UNIT_TEST_OBJS += $(UNIT_TEST_DIR)/test-lib.o
 
 # xdiff and reftable libs may in turn depend on what is in libgit.a
@@ -3189,7 +3192,9 @@ endif
 
 test_bindir_programs := $(patsubst %,bin-wrappers/%,$(BINDIR_PROGRAMS_NEED_X) $(BINDIR_PROGRAMS_NO_X) $(TEST_PROGRAMS_NEED_X))
 
-all:: $(TEST_PROGRAMS) $(test_bindir_programs) $(UNIT_TEST_PROGS)
+all:: $(TEST_PROGRAMS) $(test_bindir_programs)
+
+all:: $(UNIT_TEST_PROGS) $(UNIT_TEST_HELPER_PROGS)
 
 bin-wrappers/%: wrap-for-bin.sh
 	$(call mkdir_p_parent_template)
@@ -3620,7 +3625,7 @@ endif
 
 artifacts-tar:: $(ALL_COMMANDS_TO_INSTALL) $(SCRIPT_LIB) $(OTHER_PROGRAMS) \
 		GIT-BUILD-OPTIONS $(TEST_PROGRAMS) $(test_bindir_programs) \
-		$(UNIT_TEST_PROGS) $(MOFILES)
+		$(UNIT_TEST_PROGS) $(UNIT_TEST_HELPER_PROGS) $(MOFILES)
 	$(QUIET_SUBDIR0)templates $(QUIET_SUBDIR1) \
 		SHELL_PATH='$(SHELL_PATH_SQ)' PERL_PATH='$(PERL_PATH_SQ)'
 	test -n "$(ARTIFACTS_DIRECTORY)"
@@ -3682,7 +3687,7 @@ clean: profile-clean coverage-clean cocciclean
 	$(RM) headless-git.o
 	$(RM) $(LIB_FILE) $(XDIFF_LIB) $(REFTABLE_LIB) $(REFTABLE_TEST_LIB)
 	$(RM) $(ALL_PROGRAMS) $(SCRIPT_LIB) $(BUILT_INS) $(OTHER_PROGRAMS)
-	$(RM) $(TEST_PROGRAMS) $(UNIT_TEST_PROGS)
+	$(RM) $(TEST_PROGRAMS) $(UNIT_TEST_PROGS) $(UNIT_TEST_HELPER_PROGS)
 	$(RM) $(FUZZ_PROGRAMS)
 	$(RM) $(SP_OBJ)
 	$(RM) $(HCC)
@@ -3869,6 +3874,10 @@ $(UNIT_TEST_PROGS): $(UNIT_TEST_BIN)/%$X: $(UNIT_TEST_DIR)/%.o $(UNIT_TEST_DIR)/
 	$(QUIET_LINK)$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) \
 		$(filter %.o,$^) $(filter %.a,$^) $(LIBS)
 
+$(UNIT_TEST_HELPER_PROGS): %$X: %.o $(UNIT_TEST_DIR)/test-lib.o $(GITLIBS) GIT-LDFLAGS
+	$(QUIET_LINK)$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) \
+		$(filter %.o,$^) $(filter %.a,$^) $(LIBS)
+
 .PHONY: build-unit-tests unit-tests
 build-unit-tests: $(UNIT_TEST_PROGS)
 unit-tests: $(UNIT_TEST_PROGS)
diff --git a/t/Makefile b/t/Makefile
index b7a6fefe28..0bee7bc6ea 100644
--- a/t/Makefile
+++ b/t/Makefile
@@ -42,7 +42,7 @@ TPERF = $(sort $(wildcard perf/p[0-9][0-9][0-9][0-9]-*.sh))
 TINTEROP = $(sort $(wildcard interop/i[0-9][0-9][0-9][0-9]-*.sh))
 CHAINLINTTESTS = $(sort $(patsubst chainlint/%.test,%,$(wildcard chainlint/*.test)))
 CHAINLINT = '$(PERL_PATH_SQ)' chainlint.pl
-UNIT_TESTS = $(sort $(filter-out %.pdb unit-tests/bin/t-basic%,$(wildcard unit-tests/bin/t-*)))
+UNIT_TESTS = $(sort $(filter-out %.pdb,$(wildcard unit-tests/bin/t-*)))
 
 # `test-chainlint` (which is a dependency of `test-lint`, `test` and `prove`)
 # checks all tests in all scripts via a single invocation, so tell individual
diff --git a/t/t0080-unit-test-output.sh b/t/t0080-unit-test-output.sh
index 961b54b06c..7431023d97 100755
--- a/t/t0080-unit-test-output.sh
+++ b/t/t0080-unit-test-output.sh
@@ -8,50 +8,50 @@ test_expect_success 'TAP output from unit tests' '
 	cat >expect <<-EOF &&
 	ok 1 - passing test
 	ok 2 - passing test and assertion return 1
-	# check "1 == 2" failed at t/unit-tests/t-basic.c:76
+	# check "1 == 2" failed at t/t0080/t-basic.c:76
 	#    left: 1
 	#   right: 2
 	not ok 3 - failing test
 	ok 4 - failing test and assertion return 0
 	not ok 5 - passing TEST_TODO() # TODO
 	ok 6 - passing TEST_TODO() returns 1
-	# todo check ${SQ}check(x)${SQ} succeeded at t/unit-tests/t-basic.c:25
+	# todo check ${SQ}check(x)${SQ} succeeded at t/t0080/t-basic.c:25
 	not ok 7 - failing TEST_TODO()
 	ok 8 - failing TEST_TODO() returns 0
-	# check "0" failed at t/unit-tests/t-basic.c:30
+	# check "0" failed at t/t0080/t-basic.c:30
 	# skipping test - missing prerequisite
-	# skipping check ${SQ}1${SQ} at t/unit-tests/t-basic.c:32
+	# skipping check ${SQ}1${SQ} at t/t0080/t-basic.c:32
 	ok 9 - test_skip() # SKIP
 	ok 10 - skipped test returns 1
 	# skipping test - missing prerequisite
 	ok 11 - test_skip() inside TEST_TODO() # SKIP
 	ok 12 - test_skip() inside TEST_TODO() returns 1
-	# check "0" failed at t/unit-tests/t-basic.c:48
+	# check "0" failed at t/t0080/t-basic.c:48
 	not ok 13 - TEST_TODO() after failing check
 	ok 14 - TEST_TODO() after failing check returns 0
-	# check "0" failed at t/unit-tests/t-basic.c:56
+	# check "0" failed at t/t0080/t-basic.c:56
 	not ok 15 - failing check after TEST_TODO()
 	ok 16 - failing check after TEST_TODO() returns 0
-	# check "!strcmp("\thello\\\\", "there\"\n")" failed at t/unit-tests/t-basic.c:61
+	# check "!strcmp("\thello\\\\", "there\"\n")" failed at t/t0080/t-basic.c:61
 	#    left: "\011hello\\\\"
 	#   right: "there\"\012"
-	# check "!strcmp("NULL", NULL)" failed at t/unit-tests/t-basic.c:62
+	# check "!strcmp("NULL", NULL)" failed at t/t0080/t-basic.c:62
 	#    left: "NULL"
 	#   right: NULL
-	# check "${SQ}a${SQ} == ${SQ}\n${SQ}" failed at t/unit-tests/t-basic.c:63
+	# check "${SQ}a${SQ} == ${SQ}\n${SQ}" failed at t/t0080/t-basic.c:63
 	#    left: ${SQ}a${SQ}
 	#   right: ${SQ}\012${SQ}
-	# check "${SQ}\\\\${SQ} == ${SQ}\\${SQ}${SQ}" failed at t/unit-tests/t-basic.c:64
+	# check "${SQ}\\\\${SQ} == ${SQ}\\${SQ}${SQ}" failed at t/t0080/t-basic.c:64
 	#    left: ${SQ}\\\\${SQ}
 	#   right: ${SQ}\\${SQ}${SQ}
 	not ok 17 - messages from failing string and char comparison
-	# BUG: test has no checks at t/unit-tests/t-basic.c:91
+	# BUG: test has no checks at t/t0080/t-basic.c:91
 	not ok 18 - test with no checks
 	ok 19 - test with no checks returns 0
 	1..19
 	EOF
 
-	! "$GIT_BUILD_DIR"/t/unit-tests/bin/t-basic >actual &&
+	! "$GIT_BUILD_DIR"/t/t0080/t-basic >actual &&
 	test_cmp expect actual
 '
 
diff --git a/t/t0080/.gitignore b/t/t0080/.gitignore
new file mode 100644
index 0000000000..1903542827
--- /dev/null
+++ b/t/t0080/.gitignore
@@ -0,0 +1 @@
+/t-basic
diff --git a/t/unit-tests/t-basic.c b/t/t0080/t-basic.c
similarity index 98%
rename from t/unit-tests/t-basic.c
rename to t/t0080/t-basic.c
index fda1ae59a6..83727221b1 100644
--- a/t/unit-tests/t-basic.c
+++ b/t/t0080/t-basic.c
@@ -1,4 +1,4 @@
-#include "test-lib.h"
+#include "../unit-tests/test-lib.h"
 
 /*
  * The purpose of this "unit test" is to verify a few invariants of the unit
-- 
2.43.0.381.gb435a96ce8-goog