unit-tests: add if_test

The macro TEST only allows defining a test that consists of a single
expression.  Add a new macro, if_test, which provides a way to define
unit tests that are made up of one or more statements.

if_test allows defining self-contained tests en bloc, a bit like
test_expect_success does for regular tests.  It acts like a conditional;
the test body is executed if test_skip_all() had not been called before.

Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

.clang-format

@@ -169,6 +169,11 @@ ForEachMacros:
   - 'strmap_for_each_entry'
   - 'strset_for_each_entry'
 
+# A list of macros that should be interpreted as conditionals instead of as
+# function calls.
+IfMacros:
+  - 'if_test'
+
 # The maximum number of consecutive empty lines to keep.
 MaxEmptyLinesToKeep: 1
 

t/helper/test-example-tap.c

@@ -94,5 +94,38 @@ int cmd__example_tap(int argc, const char **argv)
 	test_res = TEST(t_empty(), "test with no checks");
 	TEST(check_int(test_res, ==, 0), "test with no checks returns 0");
 
+	if_test ("if_test passing test")
+		check_int(1, ==, 1);
+	if_test ("if_test failing test")
+		check_int(1, ==, 2);
+	if_test ("if_test passing TEST_TODO()")
+		TEST_TODO(check(0));
+	if_test ("if_test failing TEST_TODO()")
+		TEST_TODO(check(1));
+	if_test ("if_test test_skip()") {
+		check(0);
+		test_skip("missing prerequisite");
+		check(1);
+	}
+	if_test ("if_test test_skip() inside TEST_TODO()")
+		TEST_TODO((test_skip("missing prerequisite"), 1));
+	if_test ("if_test TEST_TODO() after failing check") {
+		check(0);
+		TEST_TODO(check(0));
+	}
+	if_test ("if_test failing check after TEST_TODO()") {
+		check(1);
+		TEST_TODO(check(0));
+		check(0);
+	}
+	if_test ("if_test messages from failing string and char comparison") {
+		check_str("\thello\\", "there\"\n");
+		check_str("NULL", NULL);
+		check_char('a', ==, '\n');
+		check_char('\\', ==, '\'');
+	}
+	if_test ("if_test test with no checks")
+		; /* nothing */
+
 	return test_done();
 }

t/t0080-unit-test-output.sh

@@ -50,7 +50,40 @@ test_expect_success 'TAP output from unit tests' - <<\EOT
 	# BUG: test has no checks at t/helper/test-example-tap.c:94
 	not ok 18 - test with no checks
 	ok 19 - test with no checks returns 0
-	1..19
+	ok 20 - if_test passing test
+	# check "1 == 2" failed at t/helper/test-example-tap.c:100
+	#    left: 1
+	#   right: 2
+	not ok 21 - if_test failing test
+	not ok 22 - if_test passing TEST_TODO() # TODO
+	# todo check 'check(1)' succeeded at t/helper/test-example-tap.c:104
+	not ok 23 - if_test failing TEST_TODO()
+	# check "0" failed at t/helper/test-example-tap.c:106
+	# skipping test - missing prerequisite
+	# skipping check '1' at t/helper/test-example-tap.c:108
+	ok 24 - if_test test_skip() # SKIP
+	# skipping test - missing prerequisite
+	ok 25 - if_test test_skip() inside TEST_TODO() # SKIP
+	# check "0" failed at t/helper/test-example-tap.c:113
+	not ok 26 - if_test TEST_TODO() after failing check
+	# check "0" failed at t/helper/test-example-tap.c:119
+	not ok 27 - if_test failing check after TEST_TODO()
+	# check "!strcmp("\thello\\\\", "there\"\n")" failed at t/helper/test-example-tap.c:122
+	#    left: "\011hello\\\\"
+	#   right: "there\"\012"
+	# check "!strcmp("NULL", NULL)" failed at t/helper/test-example-tap.c:123
+	#    left: "NULL"
+	#   right: NULL
+	# check "'a' == '\n'" failed at t/helper/test-example-tap.c:124
+	#    left: 'a'
+	#   right: '\012'
+	# check "'\\\\' == '\\''" failed at t/helper/test-example-tap.c:125
+	#    left: '\\\\'
+	#   right: '\\''
+	not ok 28 - if_test messages from failing string and char comparison
+	# BUG: test has no checks at t/helper/test-example-tap.c:127
+	not ok 29 - if_test test with no checks
+	1..29
 	EOF
 
 	! test-tool example-tap >actual &&

t/unit-tests/test-lib.c

@@ -16,6 +16,8 @@ static struct {
 	unsigned running :1;
 	unsigned skip_all :1;
 	unsigned todo :1;
+	char location[100];
+	char description[100];
 } ctx = {
 	.lazy_plan = 1,
 	.result = RESULT_NONE,
@@ -125,6 +127,8 @@ void test_plan(int count)
 
 int test_done(void)
 {
+	if (ctx.running && ctx.location[0] && ctx.description[0])
+		test__run_end(1, ctx.location, "%s", ctx.description);
 	assert(!ctx.running);
 
 	if (ctx.lazy_plan)
@@ -167,13 +171,38 @@ void test_skip_all(const char *format, ...)
 	va_end(ap);
 }
 
+void test__run_describe(const char *location, const char *format, ...)
+{
+	va_list ap;
+	int len;
+
+	assert(ctx.running);
+	assert(!ctx.location[0]);
+	assert(!ctx.description[0]);
+
+	xsnprintf(ctx.location, sizeof(ctx.location), "%s",
+		  make_relative(location));
+
+	va_start(ap, format);
+	len = vsnprintf(ctx.description, sizeof(ctx.description), format, ap);
+	va_end(ap);
+	if (len < 0)
+		die("unable to format message: %s", format);
+	if (len >= sizeof(ctx.description))
+		BUG("ctx.description too small to format %s", format);
+}
+
 int test__run_begin(void)
 {
+	if (ctx.running && ctx.location[0] && ctx.description[0])
+		test__run_end(1, ctx.location, "%s", ctx.description);
 	assert(!ctx.running);
 
 	ctx.count++;
 	ctx.result = RESULT_NONE;
 	ctx.running = 1;
+	ctx.location[0] = '\0';
+	ctx.description[0] = '\0';
 
 	return ctx.skip_all;
 }

t/unit-tests/test-lib.h

@@ -14,6 +14,23 @@
 	test__run_end(test__run_begin() ? 0 : (t, 1),	\
 		      TEST_LOCATION(),  __VA_ARGS__)
 
+/*
+ * Run a test unless test_skip_all() has been called.  Acts like a
+ * conditional; the test body is expected as a statement or block after
+ * the closing parenthesis.  The description for each test should be
+ * unique.  E.g.:
+ *
+ *  if_test ("something else %d %d", arg1, arg2) {
+ *          prepare();
+ *          test_something_else(arg1, arg2);
+ *          cleanup();
+ *  }
+ */
+#define if_test(...)							\
+	if (test__run_begin() ?						\
+	    (test__run_end(0, TEST_LOCATION(),  __VA_ARGS__), 0) :	\
+	    (test__run_describe(TEST_LOCATION(),  __VA_ARGS__), 1))
+
 /*
  * Print a test plan, should be called before any tests. If the number
  * of tests is not known in advance test_done() will automatically
@@ -153,6 +170,9 @@ union test__tmp {
 
 extern union test__tmp test__tmp[2];
 
+__attribute__((format (printf, 2, 3)))
+void test__run_describe(const char *, const char *, ...);
+
 int test__run_begin(void);
 __attribute__((format (printf, 3, 4)))
 int test__run_end(int, const char *, const char *, ...);