all: use ^$ instead of XXXX, NoSuchTestExists to match no tests

It's shorter and can't accidentally match unlikely test names.

Change-Id: I96dd9da018cad1acf604f266819470278f54c128
Reviewed-on: https://go-review.googlesource.com/c/go/+/524949
Auto-Submit: Dmitri Shuralyov <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
Reviewed-by: Tobias Klauser <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

Author: dmitshur

src/cmd/cgo/internal/test/issue18146.go

@@ -72,7 +72,7 @@ func test18146(t *testing.T) {
 			}()
 		}
 		runtime.GOMAXPROCS(threads)
-		argv := append(os.Args, "-test.run=NoSuchTestExists")
+		argv := append(os.Args, "-test.run=^$")
 		if err := syscall.Exec(os.Args[0], argv, os.Environ()); err != nil {
 			t.Fatal(err)
 		}

src/cmd/go/testdata/script/test_fuzz_minimize_interesting.txt

@@ -21,7 +21,7 @@ go run check_cache/check_cache.go $GOCACHE/fuzz/FuzzMinCache
 # Test that minimization occurs for a crash that appears while minimizing a
 # newly found interesting input. There must be only one worker for this test to
 # be flaky like we want.
-! exec ./fuzz.test$GOEXE -test.fuzzcachedir=$GOCACHE/fuzz -test.fuzz=FuzzMinimizerCrashInMinimization -test.run=XXX -test.fuzztime=10000x -test.parallel=1
+! exec ./fuzz.test$GOEXE -test.fuzzcachedir=$GOCACHE/fuzz -test.fuzz=FuzzMinimizerCrashInMinimization -test.run=^$ -test.fuzztime=10000x -test.parallel=1
 ! stdout '^ok'
 stdout -count=1 'got the minimum size!'
 stdout -count=1 'bad input'
@@ -32,7 +32,7 @@ go run check_testdata/check_testdata.go FuzzMinimizerCrashInMinimization 1
 
 # Test that a nonrecoverable error that occurs while minimizing an interesting
 # input is reported correctly.
-! exec ./fuzz.test$GOEXE -test.fuzzcachedir=$GOCACHE/fuzz -test.fuzz=FuzzMinimizerNonrecoverableCrashInMinimization -test.run=XXX -test.fuzztime=10000x -test.parallel=1
+! exec ./fuzz.test$GOEXE -test.fuzzcachedir=$GOCACHE/fuzz -test.fuzz=FuzzMinimizerNonrecoverableCrashInMinimization -test.run=^$ -test.fuzztime=10000x -test.parallel=1
 ! stdout '^ok'
 stdout -count=1 'fuzzing process hung or terminated unexpectedly while minimizing'
 stdout -count=1 'EOF'

src/net/http/serve_test.go

@@ -4992,7 +4992,7 @@ func benchmarkClientServerParallel(b *testing.B, parallelism int, mode testMode)
 // For use like:
 //
 //	$ go test -c
-//	$ ./http.test -test.run=XX -test.bench='^BenchmarkServer$' -test.benchtime=15s -test.cpuprofile=http.prof
+//	$ ./http.test -test.run='^$' -test.bench='^BenchmarkServer$' -test.benchtime=15s -test.cpuprofile=http.prof
 //	$ go tool pprof http.test http.prof
 //	(pprof) web
 func BenchmarkServer(b *testing.B) {
@@ -5031,7 +5031,7 @@ func BenchmarkServer(b *testing.B) {
 	defer ts.Close()
 	b.StartTimer()
 
-	cmd := testenv.Command(b, os.Args[0], "-test.run=XXXX", "-test.bench=^BenchmarkServer$")
+	cmd := testenv.Command(b, os.Args[0], "-test.run=^$", "-test.bench=^BenchmarkServer$")
 	cmd.Env = append([]string{
 		fmt.Sprintf("TEST_BENCH_CLIENT_N=%d", b.N),
 		fmt.Sprintf("TEST_BENCH_SERVER_URL=%s", ts.URL),
@@ -5086,7 +5086,7 @@ func BenchmarkClient(b *testing.B) {
 
 	// Start server process.
 	ctx, cancel := context.WithCancel(context.Background())
-	cmd := testenv.CommandContext(b, ctx, os.Args[0], "-test.run=XXXX", "-test.bench=^BenchmarkClient$")
+	cmd := testenv.CommandContext(b, ctx, os.Args[0], "-test.run=^$", "-test.bench=^BenchmarkClient$")
 	cmd.Env = append(cmd.Environ(), "TEST_BENCH_SERVER=yes")
 	cmd.Stderr = os.Stderr
 	stdout, err := cmd.StdoutPipe()

src/os/executable_test.go

@@ -30,7 +30,7 @@ func TestExecutable(t *testing.T) {
 		t.Fatalf("filepath.Rel: %v", err)
 	}
 
-	cmd := testenv.Command(t, fn, "-test.run=XXXX")
+	cmd := testenv.Command(t, fn, "-test.run=^$")
 	// make child start with a relative program path
 	cmd.Dir = dir
 	cmd.Path = fn