String & Pattern Assertions

These assertions test strings, regular expressions, and pattern matching.

to be a string

👉 See to be a string

to be a RegExp

Aliases: to be a RegExp, to be a regex, to be a regexp

Success:

expect(/hello/, 'to be a RegExp');
expect(new RegExp('world'), 'to be a regex');
expect(/[a-z]+/i, 'to be a regexp');
Copy

Failure:

expect('hello', 'to be a RegExp');
// AssertionError: Expected 'hello' to be a RegExp
Copy

Negation:

expect('hello', 'not to be a RegExp');
Copy

to begin with <string>

Aliases: to begin with <string>, to start with <string>

Success:

expect('hello world', 'to begin with', 'hello');
expect('JavaScript', 'to start with', 'Java');
Copy

Failure:

expect('hello world', 'to begin with', 'world');
// AssertionError: Expected 'hello world' to begin with 'world'
Copy

Negation:

expect('hello world', 'not to begin with', 'world');
Copy

to end with <string>

Success:

expect('hello world', 'to end with', 'world');
expect('test.js', 'to end with', '.js');
Copy

Failure:

expect('hello world', 'to end with', 'hello');
// AssertionError: Expected 'hello world' to end with 'hello'
Copy

Negation:

expect('hello world', 'not to end with', 'hello');
Copy

to match <RegExp>

Success:

expect('hello123', 'to match', /\d+/);
expect('JavaScript', 'to match', /^Java/);
expect('test@example.com', 'to match', /@/);
Copy

Failure:

expect('hello', 'to match', /\d+/);
// AssertionError: Expected 'hello' to match /\d+/
Copy

Negation:

expect('hello', 'not to match', /\d+/);
Copy

to be empty

Success:

expect('', 'to be empty');
Copy

Failure:

expect('hello', 'to be empty');
// AssertionError: Expected 'hello' to be empty
Copy

Negation:

expect('hello', 'not to be empty');
Copy

to be non-empty

Success:

expect('hello', 'to be non-empty');
expect(' ', 'to be non-empty'); // Whitespace counts as non-empty
Copy

Failure:

expect('', 'to be non-empty');
// AssertionError: Expected '' to be non-empty
Copy

Negation:

PRO TIP: Use "to be empty" instead.

expect('', 'not to be non-empty');
Copy

includes <string> / contains <string>

Aliases: includes <string>, contains <string>, to include <string>, to contain <string>

Success:

expect('hello world', 'includes', 'world');
expect('JavaScript', 'contains', 'Script');
expect([1, 2, 3], 'to include', 2);
expect('test string', 'to contain', 'string');
Copy

Failure:

expect('hello', 'includes', 'world');
// AssertionError: Expected 'hello' to include 'world'
Copy

Negation:

expect('hello', 'not to include', 'world');
Copy