tstest, util/testenv: drop tstest's dependency on the testing package

Change tstest's exported functions (AssertNotParallel, Replace,
Parallel, RequireRoot, SkipOnKernelVersions, MinAllocsPerRun, FixLogs,
UnfixLogs, CheckIsZero, ResourceCheck) to take testenv.TB instead of
testing.TB or *testing.T, so importing tstest from non-test code no
longer links the testing package and its flag registration side
effects into the binary. Add testenv.Verbose to replace the one use of
testing.Verbose, and a deptest check to keep testing out of tstest's
dependency graph.

Callers are unaffected: *testing.T and testing.TB both satisfy
testenv.TB.

Updates tailscale/corp#45223

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Change-Id: Ib373ff66ceff638d071582baf8367245987e9155

tstest/allocs.go

@@ -6,8 +6,9 @@
 import (
 	"fmt"
 	"runtime"
-	"testing"
 	"time"
+
+	"tailscale.com/util/testenv"
 )
 
 // MinAllocsPerRun asserts that f can run with no more than target allocations.
@@ -16,7 +17,7 @@
 //
 // MinAllocsPerRun sets GOMAXPROCS to 1 during its measurement and restores
 // it before returning.
-func MinAllocsPerRun(t *testing.T, target uint64, f func()) error {
+func MinAllocsPerRun(t testenv.TB, target uint64, f func()) error {
 	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(1))
 
 	var memstats runtime.MemStats

tstest/log.go

@@ -9,7 +9,6 @@
 	"log"
 	"os"
 	"sync"
-	"testing"
 
 	"go4.org/mem"
 	"tailscale.com/types/logger"
@@ -17,7 +16,7 @@
 )
 
 type testLogWriter struct {
-	t *testing.T
+	t testenv.TB
 }
 
 func (w *testLogWriter) Write(b []byte) (int, error) {
@@ -26,12 +25,12 @@ func (w *testLogWriter) Write(b []byte) (int, error) {
 	return len(b), nil
 }
 
-func FixLogs(t *testing.T) {
+func FixLogs(t testenv.TB) {
 	log.SetFlags(log.Ltime | log.Lshortfile)
 	log.SetOutput(&testLogWriter{t})
 }
 
-func UnfixLogs(t *testing.T) {
+func UnfixLogs(t testenv.TB) {
 	defer log.SetOutput(os.Stderr)
 }
 

tstest/reflect.go

@@ -6,8 +6,9 @@
 import (
 	"net/netip"
 	"reflect"
-	"testing"
 	"time"
+
+	"tailscale.com/util/testenv"
 )
 
 // IsZeroable is the interface for things with an IsZero method.
@@ -30,7 +31,7 @@ type IsZeroable interface {
 // The nonzeroValues map should contain non-zero values for each type that
 // exists in the type T or any contained types. Basic types like string, bool,
 // and numeric types are handled automatically.
-func CheckIsZero[T IsZeroable](t testing.TB, nonzeroValues map[reflect.Type]any) {
+func CheckIsZero[T IsZeroable](t testenv.TB, nonzeroValues map[reflect.Type]any) {
 	t.Helper()
 
 	var zero T

tstest/resource.go

@@ -9,8 +9,9 @@
 	"runtime/pprof"
 	"slices"
 	"strings"
-	"testing"
 	"time"
+
+	"tailscale.com/util/testenv"
 )
 
 // ResourceCheck takes a snapshot of the current goroutines and registers a
@@ -19,7 +20,7 @@
 // can look at specific routines).
 //
 // It panics if called from a parallel test.
-func ResourceCheck(tb testing.TB) {
+func ResourceCheck(tb testenv.TB) {
 	tb.Helper()
 
 	// Set an environment variable (anything at all) just for the
@@ -48,7 +49,7 @@ func ResourceCheck(tb testing.TB) {
 		// Parse and print goroutines.
 		start := parseGoroutines(startStacks)
 		end := parseGoroutines(endStacks)
-		if testing.Verbose() {
+		if testenv.Verbose() {
 			tb.Logf("goroutines start:\n%s", printGoroutines(start))
 			tb.Logf("goroutines end:\n%s", printGoroutines(end))
 		}

tstest/tstest.go

@@ -2,18 +2,23 @@
 // SPDX-License-Identifier: BSD-3-Clause
 
 // Package tstest provides utilities for use in unit tests.
+//
+// It intentionally does not depend on the "testing" package (using
+// [testenv.TB] instead of testing.TB) so that importing it from
+// non-test code doesn't link the testing package and its flag
+// registration side effects into the binary.
 package tstest
 
 import (
 	"context"
 	"fmt"
 	"os"
-	"testing"
 	"time"
 
 	"tailscale.com/envknob"
 	"tailscale.com/types/logger"
 	"tailscale.com/util/backoff"
+	"tailscale.com/util/testenv"
 )
 
 // AssertNotParallel asserts that t has not been marked as parallel.
@@ -21,7 +26,7 @@
 //
 // Use this when a test modifies package-level globals or other shared
 // state that would be unsafe to modify concurrently with other tests.
-func AssertNotParallel(t testing.TB) {
+func AssertNotParallel(t testenv.TB) {
 	t.Helper()
 	t.Setenv("ASSERT_NOT_PARALLEL_TEST", "1") // panics if t.Parallel was called
 }
@@ -32,7 +37,7 @@ func AssertNotParallel(t testing.TB) {
 // When target is a package-level variable, the caller should also call
 // [AssertNotParallel] to ensure the test is not running in parallel with
 // other tests that may access the same variable.
-func Replace[T any](t testing.TB, target *T, val T) {
+func Replace[T any](t testenv.TB, target *T, val T) {
 	t.Helper()
 	if target == nil {
 		t.Fatalf("Replace: nil pointer")
@@ -66,14 +71,14 @@ func WaitFor(maxWait time.Duration, try func() error) error {
 var serializeParallel = envknob.RegisterBool("TS_SERIAL_TESTS")
 
 // Parallel calls t.Parallel, unless TS_SERIAL_TESTS is set true.
-func Parallel(t *testing.T) {
+func Parallel(t interface{ Parallel() }) {
 	if !serializeParallel() {
 		t.Parallel()
 	}
 }
 
 // RequireRoot skips the test if the current user is not root.
-func RequireRoot(tb testing.TB) {
+func RequireRoot(tb testenv.TB) {
 	tb.Helper()
 	if os.Getuid() != 0 {
 		tb.Skip("skipping test; requires root")
@@ -82,7 +87,7 @@ func RequireRoot(tb testing.TB) {
 
 // SkipOnKernelVersions skips the test if the current
 // kernel version is in the specified list.
-func SkipOnKernelVersions(t testing.TB, issue string, versions ...string) {
+func SkipOnKernelVersions(t testenv.TB, issue string, versions ...string) {
 	major, minor, patch := KernelVersion()
 	if major == 0 && minor == 0 && patch == 0 {
 		t.Logf("could not determine kernel version")

tstest/tstest_test.go

@@ -6,8 +6,18 @@
 import (
 	"runtime"
 	"testing"
+
+	"tailscale.com/tstest/deptest"
 )
 
+func TestDeps(t *testing.T) {
+	deptest.DepChecker{
+		BadDeps: map[string]string{
+			"testing": "do not link the testing package and its flag side effects into non-test binaries; use testenv.TB",
+		},
+	}.Check(t)
+}
+
 func TestReplace(t *testing.T) {
 	before := "before"
 	done := false

util/testenv/testenv.go

@@ -22,6 +22,19 @@ func InTest() bool {
 	})
 }
 
+// Verbose reports whether the test binary is running with verbose
+// output (the -test.v flag), like testing.Verbose but without
+// importing the testing package.
+func Verbose() bool {
+	f := flag.Lookup("test.v")
+	if f == nil {
+		return false
+	}
+	// The flag's String value is "false" when off, and "true" or
+	// "test2json" when on.
+	return f.Value.String() != "false"
+}
+
 // TB is testing.TB, to avoid importing "testing" in non-test code.
 type TB interface {
 	ArtifactDir() string