Add tests for logger

Signed-off-by: Robert Lin <robertlin1@gmail.com>

internal/core/logger_test.go

@@ -0,0 +1,52 @@
+package core
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestLogger(t *testing.T) {
+	var (
+		f = "%s-%s"
+		v = []interface{}{"hello", "world"}
+		l = NewLogger()
+
+		iBuf bytes.Buffer
+		wBuf bytes.Buffer
+		eBuf bytes.Buffer
+	)
+
+	// capture output
+	l.I.SetOutput(&iBuf)
+	l.W.SetOutput(&wBuf)
+	l.E.SetOutput(&eBuf)
+
+	l.Info(v...)
+	assert.Contains(t, iBuf.String(), "[INFO]")
+	iBuf.Reset()
+
+	l.Infof(f, v...)
+	assert.Contains(t, iBuf.String(), "[INFO]")
+	assert.Contains(t, iBuf.String(), "-")
+	iBuf.Reset()
+
+	l.Warn(v...)
+	assert.Contains(t, wBuf.String(), "[WARN]")
+	iBuf.Reset()
+
+	l.Warnf(f, v...)
+	assert.Contains(t, wBuf.String(), "[WARN]")
+	assert.Contains(t, wBuf.String(), "-")
+	iBuf.Reset()
+
+	l.Error(v...)
+	assert.Contains(t, eBuf.String(), "[ERROR]")
+	iBuf.Reset()
+
+	l.Errorf(f, v...)
+	assert.Contains(t, eBuf.String(), "[ERROR]")
+	assert.Contains(t, eBuf.String(), "-")
+	iBuf.Reset()
+}