You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: user_test.go
    path of file: ./repos/upspin/user
    
    the code of the file until where you have to start completion: // Copyright 2016 The Upspin Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package
    
func TestClean(t *testing.T) {
	type cases struct {
		in  upspin.UserName
		out upspin.UserName
		ok  bool
	}
	tests := []cases{
		{"", "", false},
		{"abc@", "", false},
		{"abc@def.com", "abc@def.com", true},
		{"abc@DEF.com", "abc@def.com", true},          // lower-case the domain.
		{"e\u0302@here.com", "\u00ea@here.com", true}, // PRECIS canonicalization.
	}
	for _, test := range tests {
		out, err := Clean(test.in)
		if out == test.out && test.ok == (err == nil) {
			// All good.
			continue
		}
		if err != nil && !test.ok {
			// All good, caught the error.
			continue
		}
		t.Errorf("Clean(%q)=(%q, %v); expected %q with ok==%t", test.in, out, err, test.out, test.ok)
	}
}