unittest.mock in Python

Replacing a collaborator so a test never touches the network.

from unittest.mock import Mock, patch


def send(client, payload):
    response = client.post("/api/results", json=payload)
    return response.status_code == 200


def test_posts_the_payload():
    client = Mock()
    client.post.return_value = Mock(status_code=200)

    assert send(client, {"tpm": 104}) is True
    client.post.assert_called_once_with("/api/results", json={"tpm": 104})


def test_patches_a_name():
    with patch("time.time", return_value=1234.0) as clock:
        import time
        assert time.time() == 1234.0
    assert clock.called

How it works

1. Mock records the calls it received.
2. patch swaps a name for the duration of the block.
3. Assert on the call, not on the mock's internals.

Keywords and builtins used here

• as
• assert
• def
• return
• send
• test_patches_a_name
• test_posts_the_payload
• with

The run, in numbers

Lines

21

Characters to type

510

Tokens

126

Three-star pace

110 tpm

At the three-star pace of 110 tokens a minute, this run takes about 69 seconds.

Type this snippet

Step 2 of 3 in Selecting & faking, step 7 of 9 in Testing with pytest.

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