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Discover how to resolve float type assertion errors in JSON when testing Symfony applications using PHPUnit. Learn to implement the correct data type for your API responses.
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Fixing Float Assertion Errors in JSON with PHPUnit in Symfony

As a developer using Symfony and API Platform, you may encounter various challenges while writing tests for your API. One common issue is asserting float values through JSON responses in PHPUnit, which can often lead to frustrating errors. In this post, we will explore a specific problem related to asserting a float in JSON and provide a step-by-step solution.

The Problem

Imagine you have a Symfony application where you’ve created an entity with a float property named cost. This property is stored as double precision in your Postgres database, managed by Doctrine. During your testing phase, you decide to check if the values returned by your API are correct. Here’s an example of a test that you might write:

[[See Video to Reveal this Text or Code Snippet]]

Upon running this test, you may encounter an assertion failure that looks something like this:

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This error arises when there is a mismatch between the expected float value and the actual value returned by the API. The expected value is 25.0, but the actual value returned is just 25 (without the decimal).

Cause of the Error

The discrepancy in the representation of float values can often lead to confusion. In this case, the actual output being 25 instead of 25.0 can cause PHPUnit to fail the assertion because it treats the two values as different, even though mathematically they are equivalent.

Solution to the Problem

Change the Property Type

To resolve this issue, the ideal solution is to change the type of the cost property in your entity class. Instead of using a float type, you should switch to using a string with a type of decimal in the database. The decimal type will ensure consistent behavior when dealing with numbers that require precision, such as monetary values.

Here’s how you can implement this:

Update the Entity Class:
Change your MyEntity class as follows:

[[See Video to Reveal this Text or Code Snippet]]

Database Considerations

In the above code:

The cost property is now defined as a string.

You’re setting the type in your database to decimal with a specified precision and scale (numeric(10,2) means you can store numbers with up to 10 digits, of which 2 can be after the decimal point).

Update the Tests

After making these changes, you’ll need to ensure your tests expect a string value:

[[See Video to Reveal this Text or Code Snippet]]

This way, your test checks and confirms that the cost will be returned in the expected format as a string.

Conclusion

Dealing with float values in JSON responses can be tricky and lead to assertion errors in Symfony applications using PHPUnit. By changing the type of your property to string with a decimal format in the database, you can avoid these issues and ensure consistent and accurate API responses. Remember to update your assertions accordingly in your tests.

With this solution, you can write reliable tests for your API and ensure the integrity of your application’s data. Happy coding!