- to[.not].be.in
The in assertion determines if the actual value is present using indexOf. This
enables both strings and arrays to be used as values.
For example:
expect('def').to.be.in('abcdefgh');
expect(2).to.be.in([1, 2, 3, 4]);
The above statements are equivalent to these:
expect('abcdefgh'.indexOf('def')).to.be.ge(0);
expect([1, 2, 3, 4].indexOf(2)).to.be.ge(0);