This little Go library is designed to support file and folder 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.
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.
func Test_HelloWorld(t *testing.T) {
testdata.Setup()
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 Setup() will create
copy of your testdata folder in $TMPDIR. The Abs() function will return
absolute path to hellowold.txt.
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:
func Test_ReadString(t *testing.T) {
testdata.Setup()
var text string = testdata.ReadStr("helloworld.txt")
...
}Example how to read YAML file into structure:
type Book struct {
Title string `yaml:"title"`
Pages int `yaml:"pages"`
}
func Test_ReadString(t *testing.T) {
testdata.Setup()
book := new(Book)
testdata.ReadYAML("folder/subfolder/book.yaml", book)
...
}