8000 feat(optional assertion): add hasValueMatching method to verify predicate matches by belljun3395 · Pull Request #3863 · asser 8000 tj/assertj · GitHub
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feat(optional assertion): add hasValueMatching method to verify predicate matches#3863

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belljun3395:add-hasValueMatching-method
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feat(optional assertion): add hasValueMatching method to verify predicate matches#3863
belljun3395 wants to merge 11 commits intoassertj:mainfrom
belljun3395:add-hasValueMatching-method

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@belljun3395 belljun3395 commented Jun 22, 2025

Overview

This PR resolves issue #3848 by introducing a hasValueMatching(Predicate<T>) method to OptionalAssert. This new assertion provides a more fluent and direct way to verify that the value contained within an Optional satisfies a given predicate, enhancing the expressiveness of tests involving Optional types.

The Motivation

Currently, while ObjectAssert offers a convenient matches(Predicate) method, OptionalAssert lacks an equivalent, direct mechanism. To test a predicate against the value of an Optional, a user has to resort to less intuitive or unsafe patterns:

// This can throw a NoSuchElementException if the optional is empty.
assertThat(optional.get()).matches(MyPredicates::isAdult);

// This is safer, but more verbose than necessary.
assertThat(optional).hasValueSatisfying(value -> assertThat(value).matches(MyPredicates::isAdult));

The absence of a direct method makes the test code either less readable or less robust. This PR aims to provide a dedicated assertion that is both safe and expressive.

The Solution

To address this, hasValueMatching(Predicate) and an overloaded version with a custom description have been added to AbstractOptionalAssert, making it available to all Optional assertion classes.

The new assertion is used as follows:

Optional<Person> optional = getPerson();

// The new, more fluent assertion:
// It checks for presence and that the value matches the predicate.
assertThat(optional).hasValueMatching(Person::isAdult);

// An overloaded version with a custom description for clearer failure messages.
assertThat(optional).hasValueMatching(Person::isAdult, "is an adult");

This implementation first safely checks if a value is present in the Optional.

  • If the Optional is empty, it fails with an error indicating a value was expected.
  • If the value is present, it is evaluated against the Predicate. If the predicate test fails, an AssertionError is thrown with a descriptive message, using the existing ShouldMatch error factory to ensure consistency with other assertions in AssertJ.

This approach provides a clean, safe, and readable API for a common testing scenario.

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@belljun3395 belljun3395 changed the title feat(optional assertion): add hasValueMatching method to verify predi… feat(optional assertion): add hasValueMatching method to verify predicate matches Aug 7, 2025
@joel-costigliola joel-costigliola self-requested a review August 13, 2025 14:17
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belljun3395 commented Aug 13, 2025

@joel-costigliola I have resolved the issue introduced in this commit 😃

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joel-costigliola commented Aug 13, 2025

Thanks !

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joel-costigliola commented Aug 13, 2025

Integrated with minor edits, thanks @belljun3395 !

@joel-costigliola joel-costigliola added this to the 4.0.0-M2 milestone Aug 13, 2025
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Add OptionalAssert.hasValueMatching(Predicate<T>)

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