I am working on a react webapp and have run into a really strange issue when trying to get my unit tests to pass.

Essentially I have a javascript class called Time that's essentially just the time component of a DateTime (its based on a Luxon Duration). I have added isBefore(Time) and isAfter(Time) methods to this class to allow two times to be compared.

These methods are used in a helper function (checkTimeRange) in another file to implement a three-way comparison (i.e. it can tell if one Time is before, during, or after a range denoted by two other Times).

Here's the state of my unit tests:

• Time tests: passing, including for isAfter.
• helper tests: passing, including for checkTimeRange
• School, ClassPeriod, and BellSchedule (all classes that contain methods that indirectly depend on checkTimeRange) tests for those methods are failing because <variable storing a Time>.isAfter is not a function

In researching, I found this, which seemed to describe the issue perfectly (in the title at least), but the solution seemed to be a simple typo, which doesn't appear to be the case here.

Things I have tried:

• checking out the project in another folder
• deleting and re-installing the node_modules
• clearing the yarn cache
• updating dependencies
• changing the functions from public function name () {} syntax to arrow function (public const name = () => {}) syntax
• checking for typos and variable shadowing
• running tests both via yarn test and using the VSCode integration thats showing up in my editor (idk whats causing this to show up though)
• placing a unit test for Time.isAfter right alongside the case that is failing because isAfter is not a function to show that its not a difference in how the different unit test files are set up
• updating yarn from 1.17.3 to 1.22.19

I still have basically no idea as to what may be causing this. I have a feeling that maybe something deep inside Jest is not working properly, but I don't really know whats causing this contradicting behavior.

Here is the branch of the repo where im seeing this behavior if anyone needs more info on whats happening

The test that i'm looking at is the last one in the file of unit tests for the School class. However many of the other classes, like ClassPeriod also have their last test failing for similar reasons.

CodePudding user response：

tl;dr: <variable storing a Time> is not storing a Time.

Here is the test error.

  ● School › can check if school is in session

    TypeError: startTime.isAfter is not a function

      112 |
      113 |     // swap the values if startTime is after end time
    > 114 |     if (startTime.isAfter(endTime)) {
          |                   ^
      115 |         let t = startTime
      116 |         startTime = endTime
      117 |         endTime = t

      at checkTimeRange (src/utils/helpers.tsx:114:19)
      at School.isInSession (src/@types/school.ts:146:13)
      at Object.<anonymous> (src/@types/school.test.ts:97:23)
      at TestScheduler.scheduleTests (node_modules/@jest/core/build/TestScheduler.js:333:13)
      at runJest (node_modules/@jest/core/build/runJest.js:404:19)

I added console.log(startTime);console.log(endTime); to checkTimeRange.

startTime and endTime are both Luxon DateTimes which do not have an isAfter function. startTime.isAfter(endTime) won't work.