It is very easy to write incomplete assertions when using some test frameworks. This rule enforces complete Chai assertions in the following cases:

• when assert.fail, expect.fail or should.fail are present but not called.
• when an expect(...) or should assertion is not followed by an assertion method, such as equal.
• when an expect or should assertion ends with a chainable getters, such as .that, or a modifier, such as .deep.
• when an expect or should assertion function, such as .throw, is not called.

In such cases, what is intended to be a test doesn’t actually verify anything

Noncompliant Code Example

const assert = require('chai').assert;
const expect = require('chai').expect;

describe("incomplete assertions", function() {
    const value = 42;

    it("uses chai 'assert'", function() {
        assert.fail;  // Noncompliant
    });

    it("uses chai 'expect'", function() {
        expect(1 == 1);  // Noncompliant
        expect(value.toString).to.throw;  // Noncompliant
    });
});

Compliant Solution

const assert = require('chai').assert;
const expect = require('chai').expect;

describe("incomplete assertions", function() {
    const value = 42;

    it("uses chai 'assert'", function() {
        assert.fail();
    });

    it("uses chai 'expect'", function() {
        expect(1).to.equal(1);
        expect(value.toString).throw(TypeError);
    });
});