sn3d / tdata

Idempotent unit testing with 'testdata' folders

T-Data - testdata library

This little Go library is designed to support testdata manipulation in unit tests. It enables tests that modify files to be idempotent, meaning they will produce the same result even if run multiple times.

That's fine if you need to read files and you're not modify it. But I have tests, they're mutating files. I need some way how to ensure idempotency of tests.

Another issue that commonly arises when testing with files is that you cannot use go embed directly within your tests. Fortunately, the library provides functions like ReadStr(), ReadYAML(), and ReadJSON() that you can utilize instead. By using these functions, you can avoid having to resort to any kind of 'go embed' manipulation in your testing.

This library creates copy of your testdata folder in your $TEMPDIR, for every test run.

Basic usage

Let's assume we have helloworld_test.go and testdata folder, where is helloworld.txt. The unit test will load the text from file, append new text and save it.

import testdata "github.com/sn3d/tdata"

func Test_HelloWorld(t *testing.T) {
   testdata.Init(t)

   content, err := ioutil.ReadFile(testdata.Abs("helloworld.txt")) 
   if err != nil {
      t.FailNow()
   }

   content := fmt.Sprintf("%s hello world\n", content)

   err := ioutil.WriteFile(testdata.Abs("helloworld.txt"), []byte(content), 0644)
   if err != nil {
      t.FailNow()
   }
}

The above example is example of idempotent file test. First, the InitTestdata() will create copy of your testdata folder in $TMPDIR. The Abs() function will return absolute path to hellowold.txt.

Using Read....() functions

You can use hi-level ReadStr(), ReadYAML() or ReadJSON() functions for loading files. These functions suppose to not fail. If there is problem with file, functions will give you no data.

Example how to read file as string:

import testdata "github.com/sn3d/tdata"

func Test_ReadString(t *testing.T) {
   testadata.Init(t)

   var text string = testdata.ReadStr("helloworld.txt")

   ...
}

Example how to read YAML file into structure:

import testdata "github.com/sn3d/tdata"

type Book struct {
   Title string `yaml:"title"`
   Pages int    `yaml:"pages"`
}

func Test_ReadString(t *testing.T) {
    testdata.Init(t)

    book := new(Book)
	testdata.ReadYAML("folder/subfolder/book.yaml", book)

   ...
}