Replace stretchr/testify with an internal test suite (#981)

As recommended, an `internal/assert` package was added with a reduced set of assertions. All tests were then refactored to use the internal assertions. When more complex assertions were used, they have been rewritten using logic and the simplified assertions.

Fancy formatting for failures was omitted. The `internal/assert/assertions.diff` function could be overwritten for better formatting. That is where diff libraries are used in other test suites.

Refs: #872

Co-authored-by: Alex Mikitik <alex.mikitik@oracle.com>

internal/cli/cli_test.go

@@ -11,8 +11,7 @@ import (
 	"testing"
 
 	"github.com/pelletier/go-toml/v2"
-	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
+	"github.com/pelletier/go-toml/v2/internal/assert"
 )
 
 func processMain(args []string, input io.Reader, stdout, stderr io.Writer, f ConvertFn) int {
@@ -30,8 +29,8 @@ func TestProcessMainStdin(t *testing.T) {
 	})
 
 	assert.Equal(t, 0, exit)
-	assert.Empty(t, stdout.String())
-	assert.Empty(t, stderr.String())
+	assert.Zero(t, stdout.String())
+	assert.Zero(t, stderr.String())
 }
 
 func TestProcessMainStdinErr(t *testing.T) {
@@ -44,8 +43,8 @@ func TestProcessMainStdinErr(t *testing.T) {
 	})
 
 	assert.Equal(t, -1, exit)
-	assert.Empty(t, stdout.String())
-	assert.NotEmpty(t, stderr.String())
+	assert.Zero(t, stdout.String())
+	assert.NotZero(t, stderr.String())
 }
 
 func TestProcessMainStdinDecodeErr(t *testing.T) {
@@ -59,16 +58,16 @@ func TestProcessMainStdinDecodeErr(t *testing.T) {
 	})
 
 	assert.Equal(t, -1, exit)
-	assert.Empty(t, stdout.String())
-	assert.Contains(t, stderr.String(), "error occurred at")
+	assert.Zero(t, stdout.String())
+	assert.True(t, strings.Contains(stderr.String(), "error occurred at"))
 }
 
 func TestProcessMainFileExists(t *testing.T) {
 	tmpfile, err := ioutil.TempFile("", "example")
-	require.NoError(t, err)
+	assert.NoError(t, err)
 	defer os.Remove(tmpfile.Name())
 	_, err = tmpfile.Write([]byte(`some data`))
-	require.NoError(t, err)
+	assert.NoError(t, err)
 
 	stdout := new(bytes.Buffer)
 	stderr := new(bytes.Buffer)
@@ -78,8 +77,8 @@ func TestProcessMainFileExists(t *testing.T) {
 	})
 
 	assert.Equal(t, 0, exit)
-	assert.Empty(t, stdout.String())
-	assert.Empty(t, stderr.String())
+	assert.Zero(t, stdout.String())
+	assert.Zero(t, stderr.String())
 }
 
 func TestProcessMainFileDoesNotExist(t *testing.T) {
@@ -91,22 +90,22 @@ func TestProcessMainFileDoesNotExist(t *testing.T) {
 	})
 
 	assert.Equal(t, -1, exit)
-	assert.Empty(t, stdout.String())
-	assert.NotEmpty(t, stderr.String())
+	assert.Zero(t, stdout.String())
+	assert.NotZero(t, stderr.String())
 }
 
 func TestProcessMainFilesInPlace(t *testing.T) {
 	dir, err := ioutil.TempDir("", "")
-	require.NoError(t, err)
+	assert.NoError(t, err)
 	defer os.RemoveAll(dir)
 
 	path1 := path.Join(dir, "file1")
 	path2 := path.Join(dir, "file2")
 
 	err = ioutil.WriteFile(path1, []byte("content 1"), 0600)
-	require.NoError(t, err)
+	assert.NoError(t, err)
 	err = ioutil.WriteFile(path2, []byte("content 2"), 0600)
-	require.NoError(t, err)
+	assert.NoError(t, err)
 
 	p := Program{
 		Fn:      dummyFileFn,
@@ -115,15 +114,15 @@ func TestProcessMainFilesInPlace(t *testing.T) {
 
 	exit := p.main([]string{path1, path2}, os.Stdin, os.Stdout, os.Stderr)
 
-	require.Equal(t, 0, exit)
+	assert.Equal(t, 0, exit)
 
 	v1, err := ioutil.ReadFile(path1)
-	require.NoError(t, err)
-	require.Equal(t, "1", string(v1))
+	assert.NoError(t, err)
+	assert.Equal(t, "1", string(v1))
 
 	v2, err := ioutil.ReadFile(path2)
-	require.NoError(t, err)
-	require.Equal(t, "2", string(v2))
+	assert.NoError(t, err)
+	assert.Equal(t, "2", string(v2))
 }
 
 func TestProcessMainFilesInPlaceErrRead(t *testing.T) {
@@ -134,18 +133,18 @@ func TestProcessMainFilesInPlaceErrRead(t *testing.T) {
 
 	exit := p.main([]string{"/this/path/is/invalid"}, os.Stdin, os.Stdout, os.Stderr)
 
-	require.Equal(t, -1, exit)
+	assert.Equal(t, -1, exit)
 }
 
 func TestProcessMainFilesInPlaceFailFn(t *testing.T) {
 	dir, err := ioutil.TempDir("", "")
-	require.NoError(t, err)
+	assert.NoError(t, err)
 	defer os.RemoveAll(dir)
 
 	path1 := path.Join(dir, "file1")
 
 	err = ioutil.WriteFile(path1, []byte("content 1"), 0600)
-	require.NoError(t, err)
+	assert.NoError(t, err)
 
 	p := Program{
 		Fn:      func(io.Reader, io.Writer) error { return fmt.Errorf("oh no") },
@@ -154,11 +153,11 @@ func TestProcessMainFilesInPlaceFailFn(t *testing.T) {
 
 	exit := p.main([]string{path1}, os.Stdin, os.Stdout, os.Stderr)
 
-	require.Equal(t, -1, exit)
+	assert.Equal(t, -1, exit)
 
 	v1, err := ioutil.ReadFile(path1)
-	require.NoError(t, err)
-	require.Equal(t, "content 1", string(v1))
+	assert.NoError(t, err)
+	assert.Equal(t, "content 1", string(v1))
 }
 
 func dummyFileFn(r io.Reader, w io.Writer) error {