func runBuildpackPhase()

in internal/buildpacktest/buildpacktest.go [287:347]
46 lines of code
14 McCabe index (conditional complexity)

func runBuildpackPhase(t *testing.T, cfg *config) (bool, error) {
	temps := buildpacktestenv.SetUpTempDirs(t, cfg.codeDir)
	opts := []gcp.ContextOption{gcp.WithApplicationRoot(temps.CodeDir), gcp.WithBuildpackRoot(temps.BuildpackDir)}

	// Mock out calls to ctx.Exec, if specified
	if len(cfg.mockProcesses) > 0 {
		eCmd, err := mockprocess.NewExecCmd(cfg.mockProcesses...)
		if err != nil {
			t.Fatalf("error creating mock exec command: %v", err)
		}
		opts = append(opts, gcp.WithExecCmd(eCmd))
	}

	// Logs all ctx.Exec commands to stderr
	os.Setenv(env.DebugMode, "true")
	ctx := gcp.NewContext(opts...)

	if cfg.appPath != "" {
		// Copy apps from test data into temp code dir
		if err := fileutil.MaybeCopyPathContents(temps.CodeDir, filepath.Join(flagTestData, cfg.appPath), fileutil.AllPaths); err != nil {
			return false, fmt.Errorf("unable to copy app directory %q to %q: %v", cfg.appPath, temps.CodeDir, err)
		}
	}

	for f, c := range cfg.files {
		fn := filepath.Join(temps.CodeDir, f)

		if dir := path.Dir(fn); dir != "" {
			if err := os.MkdirAll(dir, 0744); err != nil {
				return false, fmt.Errorf("creating directory tree %s: %v", dir, err)
			}
		}

		if err := ioutil.WriteFile(fn, []byte(c), 0644); err != nil {
			return false, fmt.Errorf("writing file %s: %v", fn, err)
		}
	}

	if err := os.Chdir(temps.CodeDir); err != nil {
		return false, fmt.Errorf("changing to code dir %q: %v", temps.CodeDir, err)
	}

	if cfg.buildpackPhase == buildPhase {
		if err := cfg.buildFn(ctx); err != nil {
			return false, fmt.Errorf("build error: %v", err)
		}
	} else {
		detect, err := cfg.detectFn(ctx)
		if err != nil {
			return false, fmt.Errorf("detect error: %v", err)
		}

		// Mimics the exit code of libcnb library when the detect function
		// succeeds but does not pass detect.
		if !detect.Result().Pass {
			return false, nil
		}
	}

	return true, nil
}