Present validation errors consistently in the CLI

cmd/releasekit/main_test.go

@@ -97,6 +97,58 @@ func TestCheckCommandBindsConfiguredChecksToCapturedCandidate(t *testing.T) {
 	}
 }
 
+func TestCandidateCommandsPresentValidationDiagnosticsOnce(t *testing.T) {
+	repository := newCLIRepository(t)
+	profile, err := json.Marshal(cli.Settings{Product: "Example Product"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	writeRepositoryFile(t, repository, "releasekit.json", string(profile))
+	cliGitRun(t, repository, "add", "releasekit.json")
+	cliGitRun(t, repository, "commit", "-m", "configure candidate commands")
+	remote := filepath.Join(t.TempDir(), "origin.git")
+	cliGitRun(t, repository, "init", "--bare", remote)
+	cliGitRun(t, repository, "remote", "add", "origin", remote)
+	cliGitRun(t, repository, "push", "origin", "HEAD:refs/heads/main")
+
+	goPath, err := exec.LookPath("go")
+	if err != nil {
+		t.Fatal(err)
+	}
+	goDirectory := t.TempDir()
+	shim := filepath.Join(goDirectory, "go")
+	if err := os.WriteFile(shim, []byte("#!/bin/sh\nif [ \"$1\" = test ]; then echo 'fixture Go suite failure' >&2; exit 1; fi\nexec \"$RELEASEKIT_REAL_GO\" \"$@\"\n"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	t.Setenv("RELEASEKIT_REAL_GO", goPath)
+	t.Setenv("PATH", goDirectory+string(os.PathListSeparator)+os.Getenv("PATH"))
+
+	for _, command := range []struct {
+		name       string
+		wantStatus int
+		args       []string
+	}{
+		{name: "check", wantStatus: 1, args: []string{"check", "--repo", repository, "v1.2.3"}},
+		{name: "publish", wantStatus: 1, args: []string{"publish", "--repo", repository, "v1.2.3"}},
+	} {
+		t.Run(command.name, func(t *testing.T) {
+			var stdout, stderr bytes.Buffer
+			if status := run(context.Background(), command.args, &stdout, &stderr); status != command.wantStatus {
+				t.Fatalf("run() status = %d; stdout=%q stderr=%q", status, stdout.String(), stderr.String())
+			}
+			if got := strings.Count(stderr.String(), "go-test validation failed"); got != 1 {
+				t.Fatalf("validation diagnostic appeared %d times: %q", got, stderr.String())
+			}
+			if !strings.Contains(stderr.String(), "fixture Go suite failure") {
+				t.Fatalf("stderr omitted the validation cause: %q", stderr.String())
+			}
+			if command.name == "publish" && !strings.Contains(stderr.String(), "state=not_attempted phase=validation") {
+				t.Fatalf("publication validation error lost its state: %q", stderr.String())
+			}
+		})
+	}
+}
+
 func TestPublishCommandPublishesConfiguredCandidate(t *testing.T) {
 	repository := newCLIRepository(t)
 	writeRepositoryFile(t, repository, "docs/releases/v1.2.3.md", "# Example Product v1.2.3\n\n## Compatibility\n\nNo action required.\n")