test: Use modern testing features instead of custom helpers

Many of our tests rely on helpers that predate features which are now
available in the standard library.

This patch replaces them with the standard equivalents:

- MustTempDir/RemoveIfOk -> t.ArtifactDir() or t.TempDir() (depending on
  whether it is useful to keep the data on request).
- GetFreePort + waitForServer -> opening the listeners before starting
  the servers. To support this, localrpc.Server gains a Serve method. We
  may re-introduce these in the future if more use cases appear.
- WaitFor and real-time timing checks -> testing/synctest.
- context.Background() -> t.Context().
- Benchmark b.N loops -> b.Loop().
- reflect.DeepEqual -> cmp.Diff, and proto.Equal for protobufs.

internal/sts/sts_test.go

@@ -72,7 +72,7 @@ func TestMain(m *testing.M) {
 	httpServer := httptest.NewServer(http.HandlerFunc(testHTTPHandler))
 
 	fakeURLForTesting = httpServer.URL
-	os.Exit(m.Run())
+	m.Run()
 }
 
 func TestParsePolicy(t *testing.T) {
@@ -196,21 +196,21 @@ func TestFetch(t *testing.T) {
 	// defined in TestMain above. See httpGet for more details.
 
 	// Normal fetch, all valid.
-	p, err := Fetch(context.Background(), "domain.com")
+	p, err := Fetch(t.Context(), "domain.com")
 	if err != nil {
 		t.Errorf("failed to fetch policy: %v", err)
 	}
 	t.Logf("domain.com: %+v", p)
 
 	// Domain without a policy (HTTP get fails).
-	p, err = Fetch(context.Background(), "policy404")
+	p, err = Fetch(t.Context(), "policy404")
 	if err == nil {
 		t.Errorf("fetched unknown policy: %v", p)
 	}
 	t.Logf("policy404: got error as expected: %v", err)
 
 	// Domain with an invalid policy (unknown version).
-	p, err = Fetch(context.Background(), "version99")
+	p, err = Fetch(t.Context(), "version99")
 	if err != ErrUnknownVersion {
 		t.Errorf("expected error %v, got %v (and policy: %v)",
 			ErrUnknownVersion, err, p)
@@ -218,7 +218,7 @@ func TestFetch(t *testing.T) {
 	t.Logf("version99: got expected error: %v", err)
 
 	// Error fetching TXT record for this domain.
-	p, err = Fetch(context.Background(), "domErr")
+	p, err = Fetch(t.Context(), "domErr")
 	if err != errTest {
 		t.Errorf("expected error %v, got %v (and policy: %v)",
 			errTest, err, p)
@@ -235,7 +235,7 @@ func TestPolicyTooBig(t *testing.T) {
 	raw += `"mxlast"], "max_age": 100}`
 	policyForDomain["toobig"] = raw
 
-	_, err := Fetch(context.Background(), "toobig")
+	_, err := Fetch(t.Context(), "toobig")
 	if err == nil {
 		t.Errorf("fetch worked, but should have failed")
 	}
@@ -251,8 +251,7 @@ func expvarMustEq(t *testing.T, name string, v *expvar.Int, expected int64) {
 }
 
 func TestCacheBasics(t *testing.T) {
-	dir := testlib.MustTempDir(t)
-	defer testlib.RemoveIfOk(t, dir)
+	dir := t.ArtifactDir()
 
 	c, err := NewCache(dir)
 	if err != nil {
@@ -266,7 +265,7 @@ func TestCacheBasics(t *testing.T) {
 	cacheFetches.Set(0)
 	cacheHits.Set(0)
 
-	ctx := context.Background()
+	ctx := t.Context()
 
 	// Fetch domain.com, check we get a reasonable policy, and that it's a
 	// cache miss.
@@ -314,15 +313,14 @@ func TestCacheBasics(t *testing.T) {
 
 // Test how the cache behaves when the files are corrupt.
 func TestCacheBadData(t *testing.T) {
-	dir := testlib.MustTempDir(t)
-	defer testlib.RemoveIfOk(t, dir)
+	dir := t.ArtifactDir()
 
 	c, err := NewCache(dir)
 	if err != nil {
 		t.Fatal(err)
 	}
 
-	ctx := context.Background()
+	ctx := t.Context()
 
 	cacheUnmarshalErrors.Set(0)
 	cacheInvalid.Set(0)
@@ -391,6 +389,7 @@ func (c *PolicyCache) mustFetch(ctx context.Context, t *testing.T, d string) *Po
 }
 
 func mustRewriteAndChtime(t *testing.T, fname, content string) {
+	t.Helper()
 	testlib.Rewrite(t, fname, content)
 
 	// Advance the expiration time to the future, so the rewritten policy is
@@ -403,15 +402,14 @@ func mustRewriteAndChtime(t *testing.T, fname, content string) {
 }
 
 func TestCacheRefresh(t *testing.T) {
-	dir := testlib.MustTempDir(t)
-	defer testlib.RemoveIfOk(t, dir)
+	dir := t.ArtifactDir()
 
 	c, err := NewCache(dir)
 	if err != nil {
 		t.Fatal(err)
 	}
 
-	ctx := context.Background()
+	ctx := t.Context()
 
 	txtResults["_mta-sts.refresh-test"] = []string{"v=STSv1; id=blah;"}
 	policyForDomain["refresh-test"] = `
@@ -439,7 +437,7 @@ func TestCacheRefresh(t *testing.T) {
 
 	// Launch background refreshes, and wait for one to complete.
 	cacheRefreshCycles.Set(0)
-	ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
+	ctx, cancel := context.WithTimeout(t.Context(), 1*time.Second)
 	defer cancel()
 	go c.PeriodicallyRefresh(ctx)
 	for cacheRefreshCycles.Value() == 0 {
@@ -453,7 +451,7 @@ func TestCacheRefresh(t *testing.T) {
 }
 
 func TestCacheSlashSafe(t *testing.T) {
-	dir := testlib.MustTempDir(t)
+	dir := t.ArtifactDir()
 	c, err := NewCache(dir)
 	if err != nil {
 		t.Fatal(err)
@@ -519,7 +517,7 @@ func TestHTTPGet(t *testing.T) {
 		}))
 	defer srv1.Close()
 
-	ctx := context.Background()
+	ctx := t.Context()
 	raw, err := httpGet(ctx, srv1.URL)
 	if err != nil {
 		t.Errorf("GET failed: got %q, %v", raw, err)