chore: add test case for source/function of recovery.go (#1467)

recovery_test.go

@@ -41,3 +41,23 @@ func TestPanicWithAbort(t *testing.T) {
 	// TEST
 	assert.Equal(t, 400, w.Code)
 }
+
+func TestSource(t *testing.T) {
+	bs := source(nil, 0)
+	assert.Equal(t, []byte("???"), bs)
+
+	in := [][]byte{
+		[]byte("Hello world."),
+		[]byte("Hi, gin.."),
+	}
+	bs = source(in, 10)
+	assert.Equal(t, []byte("???"), bs)
+
+	bs = source(in, 1)
+	assert.Equal(t, []byte("Hello world."), bs)
+}
+
+func TestFunction(t *testing.T) {
+	bs := function(1)
+	assert.Equal(t, []byte("???"), bs)
+}