Improved support for BigInts

Oct 13, 2025 by pinkandtrash.com 19 views

Introduction

The testharness.js library is a widely used testing framework for web applications. It provides a set of assertion functions to verify the expected behavior of a test. However, the current implementation of these assertion functions has a limitation when it comes to working with BigInts. In this article, we will discuss the issue and propose a solution to support BigInts in the assert_greater_than(), assert_less_than(), assert_less_than_equal(), assert_greater_than_equal(), and assert_between_exclusive() functions.

The Issue

The problem arises when trying to compare two BigInt values using the relational operators (>, <, >=, <=). The typeof operator returns "bigint" for BigInt values, which is not equal to "number". This causes the assertion functions to fail when trying to compare two BigInt values.

For example, if we try to assert that 2n is greater than 1n using the assert_greater_than() function, we get a failure message "expected a number but got a bigint". This is because the typeof operator returns "bigint" for the 2n value, which is not equal to "number".

Relevant Functions

The following assertion functions are affected by this issue:

assert_less_than(): Verifies that the actual value is less than the expected value.
assert_greater_than(): Verifies that the actual value is greater than the expected value.
assert_less_than_equal(): Verifies that the actual value is less than or equal to the expected value.
assert_greater_than_equal(): Verifies that the actual value is greater than or equal to the expected value.
assert_between_exclusive(): Verifies that the actual value is within a specified range (exclusive).
assert_between_inclusive(): Verifies that the actual value is within a specified range (inclusive).

Context

The issue is not just limited to the testharness.js library. There are other testing frameworks and libraries that also rely on these assertion functions. For example, the WebNN test helper uses the > comparison operator to verify the expected behavior of a test. However, since the values being compared are often BigInts, the assert_less_than_equal() function cannot be used.

Proposed Solution

To support BigInts in the assertion functions, we can modify the typeof operator check to allow both "number" and "bigint" values. This will enable the comparison of BigInt values using the relational operators.

Here is an updated implementation of the assert_greater_than() function:

function assert_greater_than(actual, expected) {
  if (typeof actual === "bigint" || typeof actual === "number") {
    if (actual > expected) {
      return true;
    } else {
      return false;
    }
  } else {
    throw new Error("Expected a number or bigint, but got " + typeof actual);
  }
}

Similarly, we can update the other assertion functions to support BigInts.

Benefits

The proposed solution has several benefits:

Improved support for BigInts: The updated assertion functions will be able to handle BigInt values correctly, enabling more accurate testing of web applications.
Increased flexibility: The modified typeof operator check will allow for more flexibility when comparing values, making it easier to write tests for complex scenarios.
Better error messages: The updated error messages will provide more informative information about the failure, making it easier to diagnose and fix issues.

Conclusion

Introduction

In our previous article, we discussed the issue of supporting BigInts in the testharness.js library. We proposed a solution to modify the typeof operator check to allow both "number" and "bigint" values. In this article, we will answer some frequently asked questions (FAQs) about the proposed solution.

Q: Why is this issue important?

A: The issue is important because BigInts are a new data type in JavaScript that allows for larger integer values. Many web applications use BigInts to represent large numbers, and the testharness.js library is widely used for testing these applications. Without support for BigInts, the library will fail to accurately test these applications, leading to potential bugs and issues.

Q: How will this change affect the `testharness.js` library?

A: The change will affect the testharness.js library by allowing it to correctly compare BigInt values using the relational operators (>, <, >=, <=). This will enable more accurate testing of web applications that use BigInts.

Q: Will this change break existing tests?

A: No, the change will not break existing tests. The updated typeof operator check will only affect tests that use BigInt values, and will not affect tests that use only numbers.

Q: How will this change affect the error messages?

A: The change will affect the error messages by providing more informative information about the failure. Instead of the generic "expected a number but got a bigint" error message, the updated error message will indicate that the actual value is a BigInt and that it is not equal to the expected value.

Q: Can I use this change with other testing frameworks?

A: Yes, the change can be used with other testing frameworks that rely on the testharness.js library. The updated typeof operator check is a generic solution that can be applied to any testing framework that uses the testharness.js library.

Q: How can I implement this change in my own testing framework?

A: To implement this change in your own testing framework, you can follow these steps:

Update the typeof operator check to allow both "number" and "bigint" values.
Modify the assertion functions to use the updated typeof operator check.
Test your updated testing framework to ensure that it correctly handles BigInt values.

Q: What are the benefits of this change?

A: The benefits of this change include:

Improved support for BigInts: The updated assertion functions will be able to handle BigInt values correctly, enabling more accurate testing of web applications.
Increased flexibility: The modified typeof operator check will allow for more flexibility when comparing values, making it easier to write tests for complex scenarios.
Better error messages: The updated error messages will provide more informative information about the failure, making it easier to diagnose and fix issues.

Conclusion

In conclusion, the proposed solution to support BigInts in the testharness.js library is a significant improvement that will enable more accurate testing of web applications. By answering some frequently asked questions, we have provided a better understanding of the issue and the proposed solution. We hope that this article has been helpful in addressing any questions or concerns you may have had about the proposed solution.