Capture Golang Zap logger output for unit tests

capture_zap_output.go

import (
  "bufio"
  "go.uber.org/zap"
  "go.uber.org/zap/zapcore"
)


/*
Global Logger variable is a Zap logger.

USAGE:
    output := captureOutput(func() {
        Logger.Info("Stuff")
    })
    
    // output contains the log entry
*/


func captureOutput(funcToRun func()) string {
    var buffer bytes.Buffer

    oldLogger := Logger

    encoder := zapcore.NewConsoleEncoder(zap.NewDevelopmentEncoderConfig())
    writer := bufio.NewWriter(&buffer)

    Logger = zap.New(
        zapcore.NewCore(encoder, zapcore.AddSync(writer), zapcore.DebugLevel)).
        Sugar()

    funcToRun()
    writer.Flush()

    Logger = oldLogger

    return buffer.String()
}