Quick Start

You can use Rehearser to build reliable unit tests quickly

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Tutorials:

• Introduction
• Step-by-step

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Development Flow:

graph LR

R["Rehearsal<br>runs"]--"interactions<br>file<br>case 1"-->A1["Adjust your<br>expectation"]-->C1["Create<br>Mocks"]-->U1("Unit Test 1")-->F["Finalize<br>Implementation"]
R["Rehearsal<br>runs"]--"interactions<br>file<br>case 2"-->A2["Adjust your<br>expectation"]-->C2["Create<br>Mocks"]-->U2("Unit Test 2")-->F["Finalize<br>Implementation"]
R["Rehearsal<br>runs"]--"interactions<br>file<br>case ..."-->A3["Adjust your<br>expectation"]-->C3["Create<br>Mocks"]-->U3("Unit Test ...")-->F["Finalize<br>Implementation"]
R["Rehearsal<br>runs"]--"interactions<br>file<br>case N"-->AN["Adjust your<br>expectation"]-->CN["Create<br>Mocks"]-->UN("Unit Test N")-->F["Finalize<br>Implementation"]

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Install Rehearser:

pip install -U rehearser

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Example 1: Mock a method:

from unittest.mock import Mock, patch

from rehearser.mock_generator import MockGenerator
from rehearser.rehearser_method import RehearserMethod


def long_run_method(x):
    print(f"Take a long time to run in {x*x} days...")
    return x*x


# Run a Rehearsal
rehearser = RehearserMethod(long_run_method)
with patch("__main__.long_run_method", rehearser):
    a=long_run_method(1)
    b=long_run_method(2)
    c=long_run_method(3)
    
    # Your logic
    res = a + b + c
    print(res)


# Prepare interactions files
rehearser.interactions_file_directory="./rehearser_examples/examples/example1/tests/raw_files/"
rehearser.write_interactions_to_file()


# Unit test
mock = MockGenerator(
    interactions_src="./rehearser_examples/examples/example1/tests/raw_files/long_run_method/latest_interactions.json"
).create_mock()
with patch("__main__.long_run_method", mock):
    # Replay the long time running method output with the mocked method
    a=long_run_method(1)
    b=long_run_method(2)
    c=long_run_method(3)
    
    # Your logic to be tested:
    result = a + b + c

    print(f"Result from mockers: {result} where mocked a={a}, mocked b={b}, and mocked c={c}")
    # Verify the result
    assert res == 14

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Example 2: Mock an instance:

from unittest.mock import Mock, patch

from rehearser.mock_generator import MockGenerator
from rehearser.rehearser_proxy import RehearserProxy


class ExternalService:
    def __init__(self):
        pass

    def long_run_method(self, x):
        print(f"Take a long time to run in {x*x} days...")
        return x * x


# Run a Rehearsal
rehearser = RehearserProxy(ExternalService())
with patch("__main__.ExternalService", return_value=rehearser):
    service = ExternalService()
    a = service.long_run_method(1)
    b = service.long_run_method(2)
    c = service.long_run_method(3)

    # Your logic
    res = a + b + c
    print(res)


# Prepare interactions files
rehearser.interactions_file_directory="./rehearser_examples/examples/example2/tests/raw_files/"
rehearser.write_interactions_to_file()


# Unit test
mock = MockGenerator(
    interactions_src="./rehearser_examples/examples/example2/tests/raw_files/ExternalService/latest_interactions.json"
).create_mock()
with patch("__main__.ExternalService", return_value=mock):
    # Replay the external service output with the mocked object
    service = ExternalService()
    a = service.long_run_method(1)
    b = service.long_run_method(2)
    c = service.long_run_method(3)

    # Your logic to be tested:
    result = a + b + c

    print(
        f"Result from mockers: {result} where mocked a={a}, mocked b={b}, and mocked c={c}"
    )
    # Verify the result
    assert res == 14