Use testify package for unit tests

[lazysegtree]

Library https://github.com/stretchr/testify.
It will add a depedency, but thats worth it.

• Much less bloated and much more readable tests and, hence high maintainability
• Standard in golang libraries
• Automatic diff formatting

Example

func TestFilterLine_FiltersEachLineThroughSuppliedFunction(t *testing.T) {
	t.Parallel()
	input := "hello\nworld"
	want := "HELLO\nWORLD\n"
	got, err := script.Echo(input).FilterLine(strings.ToUpper).String()
	if err != nil {
		t.Fatal(err)
	}
	if want != got {
		t.Error(cmp.Diff(want, got))
	}
}

becomes

func TestFilterLine_FiltersEachLineThroughSuppliedFunction(t *testing.T) {
	t.Parallel()
	input := "hello\nworld"
	want := "HELLO\nWORLD\n"
	got, err := script.Echo(input).FilterLine(strings.ToUpper).String()
	require.NoError(t, err)
	assert.Equal(t, want, got)
}

@bitfield Let me know what you think about this.

[lazysegtree]

Saw this now. :)

It no big deal to add a "test-time" dependency. I am sure it will save time and cognitive load for contributors, and maintainers.

But I dont have a strong opinion and don't want to harp on it.

Feel free to close the issue.

[bitfield]

Yes, thanks for the suggestion, but I think let's stick with the standard library test API for now—it's one less thing for new contributors to have to learn.

[lazysegtree]

it's one less thing for new contributors to have to learn.

That cannot justify not using it.
First, the library has an almost non-existent learning curve.
Second, someone who is contributing here will have this much skill.

It actually makes the job of new contributors easier, as they have a nicer and more readable codebase.