testutil

testutil provides test-only helpers for forcing I/O failures on demand, capturing process output, bootstrapping HTTP handlers, and normalizing time-variant values in assertions.

Table of contents

Part of nurago, a collection of independent Go packages for backend services.

import "github.com/tecnickcom/nurago/pkg/testutil"

Package testutil provides test-only helpers for forcing I/O failures on demand, capturing process output, bootstrapping HTTP handlers, and normalizing time-variant values in assertions.

Helpers

  • Deterministic I/O failure mocks: NewErrorReader returns a reader whose ErrorReader.Read always fails; NewErrorCloser returns an io.ReadCloser whose ErrorCloser.Close always fails. These exercise error paths that are otherwise difficult to trigger.
  • HTTP test bootstrap: RouterWithHandler builds an http.Handler backed by julienschmidt/httprouter with a route pre-registered.
  • Output capture for assertions: CaptureOutput redirects stdout, stderr, and the default logger for the duration of a function call and returns captured output as a string.
  • Time-variant text normalization: ReplaceDateTime and ReplaceUnixTimestamp replace dynamic timestamp fragments in strings (for example JSON responses).

Usage

reader := testutil.NewErrorReader("read failed")
closer := testutil.NewErrorCloser("close failed")
_ = reader
_ = closer

output := testutil.CaptureOutput(t, func() {
    fmt.Println("hello")
})

h := testutil.RouterWithHandler(http.MethodGet, "/health", func(w http.ResponseWriter, _ *http.Request) {
    w.WriteHeader(http.StatusOK)
})
_ = h

normalized := testutil.ReplaceDateTime(responseBody, "<DATETIME>")
normalized = testutil.ReplaceUnixTimestamp(normalized, "<UNIX_TS>")
_ = output
_ = normalized

These functions are intended for use in tests only.

When To Use

  • An error branch depends on a failing Read or Close that is hard to trigger otherwise.
  • A JSON assertion contains a generated timestamp that must be normalized first.
  • A handler needs a real router because it reads path parameters.

Example

// A JSON response carrying a generated timestamp cannot be compared
// against a fixed golden value until the timestamp is normalized.
body := `{"id":"7","created_at":"2026-09-07T15:04:05.123Z","status":"ok"}`

fmt.Println(testutil.ReplaceDateTime(body, "<TIME>"))

// Output:
// {"id":"7","created_at":"<TIME>","status":"ok"}

Full source is in example_testutil_test.go. More runnable examples are on pkg.go.dev.

Dependencies

Importing this package pulls 3 external modules:

  • github.com/julienschmidt/httprouter
  • github.com/stretchr/testify
  • go.yaml.in/yaml/v3