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title:
  - value: |
      Testing multiple implementations with contract tests
created:
  - value: '2023-08-24T00:00:00+00:00'
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  - value: '2025-05-11T09:00:34+00:00'
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      <p>If you have multiple implementations of a service, as I <a href="/daily/2023/08/23/dont-use-third-party-services-directly">mentioned in yesterday's email</a>, you need to ensure they all provide the same functionality.</p>

      <p>You need to be able to run the same tests against each implementation and have them pass.</p>

      <h2 id="how-do-you-do-this%3F">How do you do this?</h2>

      <p>In PHP, I use a trait that contains the test methods and then have a test class for each implementation that uses the trait and sets up any test data.</p>

      <p>Then, each test class will run the methods from the contract test trait and ensure they all provide the same behaviour, regardless of how it does so - whether it communicates with an API, uses an SDK, or returns fake values.</p>

      <p>If one implementation doesn't return the same result as the others, its test will fail.</p>

      <p>If you add a new implementation, you create a new test class, use the trait and get the tests to pass.</p>

              
    format: full_html
    processed: |
      <p>If you have multiple implementations of a service, as I <a href="http://default/daily/2023/08/23/dont-use-third-party-services-directly">mentioned in yesterday's email</a>, you need to ensure they all provide the same functionality.</p>

      <p>You need to be able to run the same tests against each implementation and have them pass.</p>

      <h2 id="how-do-you-do-this%3F">How do you do this?</h2>

      <p>In PHP, I use a trait that contains the test methods and then have a test class for each implementation that uses the trait and sets up any test data.</p>

      <p>Then, each test class will run the methods from the contract test trait and ensure they all provide the same behaviour, regardless of how it does so - whether it communicates with an API, uses an SDK, or returns fake values.</p>

      <p>If one implementation doesn't return the same result as the others, its test will fail.</p>

      <p>If you add a new implementation, you create a new test class, use the trait and get the tests to pass.</p>

              
    summary: null
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