test: pin the production receive limits, split the vacuous drain test, harden the lint-gate test (review of #55)

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

test/lintgate/lintgate_test.go

@@ -53,12 +53,17 @@ func hasSkipNotice(out string) bool {
 
 // runLint runs `task lint` in dir with the given PATH and returns its combined output and exit code.
 func runLint(t *testing.T, dir, path string) (string, int) {
+	t.Helper()
+	return runTask(t, dir, path, "lint")
+}
+
+func runTask(t *testing.T, dir, path string, args ...string) (string, int) {
 	t.Helper()
 	taskBin, err := exec.LookPath("task")
 	if err != nil {
 		t.Skip("task not installed")
 	}
-	cmd := exec.Command(taskBin, "lint")
+	cmd := exec.Command(taskBin, args...)
 	cmd.Dir = dir
 	cmd.Env = append(os.Environ(), "PATH="+path)
 	var out bytes.Buffer
@@ -87,6 +92,20 @@ func TestTaskLint_ExitsNonZeroWhenGolangciLintReportsAFinding(t *testing.T) {
 	if hasSkipNotice(out) {
 		t.Fatalf("task lint blamed a missing binary for a lint failure; output:\n%s", out)
 	}
+	if !strings.Contains(out, "errcheck") {
+		t.Fatalf("a non-zero exit without the finding means the linter crashed, not that it found something; output:\n%s", out)
+	}
+}
+
+// The lint step only gates anything if `task check` runs it.
+func TestTaskCheck_RunsTheLintStep(t *testing.T) {
+	out, code := runTask(t, scratchModule(t), os.Getenv("PATH"), "--dry", "check")
+	if code != 0 {
+		t.Fatalf("task --dry check exited %d; output:\n%s", code, out)
+	}
+	if !strings.Contains(out, "task: [lint]") {
+		t.Fatalf("task check no longer runs the lint step; output:\n%s", out)
+	}
 }
 
 func TestTaskLint_SkipsWithANoticeWhenGolangciLintIsAbsent(t *testing.T) {