spruce

README

Spruce

Spruce pretty-prints Go structured logs as test output.

Spruce provides an slog.Handler implementation that acts as an adaptor between an slog.Logger and the testing.TB interface.

Example Usage

package pkg_test

import (
    "log/slog"
    "testing"

    "github.com/dogmatiq/spruce"
)

func TestSomething(t *testing.T) {
    // Create a new spruce logger that directs logs to t.
    logger := spruce.NewLogger(t)

    // Run the application code that is being tested, and direct its log output
    // to the test log.
    systemUnderTest(logger)
}

// systemUnderTest is your existing application code that uses an [slog.Logger].
func systemUnderTest(logger *slog.Logger) {
    // Log a message with some complex structured attributes.
    logger.Info(
		"hello, world!",
		slog.Group(
			"<group b>",
			"<key-1>", "<value-1>",
            "<key-2>", "<value-2>",
		),
		slog.Group(
			"<group a>",
			"<key-1>", "<value-1>",
		),
	)
}

The above test produces the following output:

spruce.go:76: [INFO] hello, world!
    ├─┬ <group b>
    │ ├── <key-1> ┈ <value-1>
    │ ╰── <key-2> ┈ <value-2>
    ╰─┬ <group a>
      ╰── <key-1> ┈ <value-1>

Documentation

Overview

Package spruce providers an slog.Handler that writes pretty-printed structured logs to a testing.T (or compatible) logger.

Index

• func NewHandler(t TestingT) slog.Handler
• func NewLogger(t TestingT) *slog.Logger
• type TestingT

Functions

func NewHandler

func NewHandler(t TestingT) slog.Handler

NewHandler returns a new slog.Handler that writes to t.

func NewLogger

func NewLogger(t TestingT) *slog.Logger

NewLogger returns a slog.Logger that writes to t.

Types

type TestingT

type TestingT interface {
	Log(...any)
}

TestingT is the subset of the testing.TB interface that is used to write logs.