Jest typeerror is not a function [SOLVED]

Searching for a solution to solve the “jest typeerror is not a function“?

Stop your search now and read through the end of this article.

In this article, you will be able to understand this error and learn how to solve it.

So, without prolonging our introduction, let us proceed to know this error message.

What is jest typeerror is not a function?

The typeerror: is not a function is an error message that could appear while using the JavaScript testing framework Jest.

The mentioned error occurs when we attempt to call a function on an undefined value.

Apart from that, it also occurs when we try to access a property of a non-object type.

What is Jest?

The JavaScript testing framework, Jest, is an open-source tool that was developed by Facebook.

Jest is used to create and execute automated tests for JavaScript applications.

Additionally, it is being used to test applications, libraries, and other JS code in the JS community.

Now that we have a better understanding of the error “jest typeerror is not a function,” let us move on to our solution.

Jest typeerror is not a function – SOLUTION

Time needed: 2 minutes

Here is the guide to solving the “jest typeerror is not a function“:

  1. Review the function call’s syntax.

    The first step is to review the syntax of the function call.

    It is to verify if the function call’s syntax is correct and matches the function signature.

  2. Confirm if the function is defined properly and is accessible.

    Make sure that in the test file, the file where the function is defined is properly imported.

  3. Double-check the type and format of the value being passed as an argument.

    Make sure it is correct and has all the needed properties.

  4. Use the async/await syntax or the .then() method.

    Use any of them to handle the promise correctly.

    Use them if the function is asynchronous and returns a promise.

  5. Debug your code.

    Do this if the error still persists.

    To debug, log values and step through your code.

    It is to distinguish the point at which the error happens.

See also: Typeerror: ‘newline’ is an invalid keyword argument for this function

Tips to avoid getting Typeerrors

The following are some tips to avoid getting type errors in Python.

  • Avoid using the built-in data types in Python in the wrong way.

    → Be sure that your variables and data structures are using the correct data types.
  • Always check or confirm the types of your variables.

    → To check the types of your variables, use the type() function.

    This will allow you to confirm if the type of your variable is appropriate.
  • Be clear and concise when writing code.

    → Being clear and concise when writing your code can help you avoid typeerrors.

    It is because it will become easier to understand.
  • Handle the error by using try-except blocks.

    → Try using the try-except blocks to catch and handle any typeerror.
  • Use the built-in functions of Python if needed.

    → Use built-in functions such as int()str(), etc. if you need to convert a variable to a different type.


What is TypeError?

Typeerror is an error in Python that arises when an operation or function is applied to a value of an improper type.

This error indicates that the data type of an object isn’t compatible with the operation or function that is being used.

What is Python?

Python is one of the most popular programming languages.

It is used for developing a wide range of applications.

In addition, Python is a high-level programming language that is used by most developers due to its flexibility.


In conclusion, the “jest typeerror is not a function” occurs when we attempt to call a function on a value that is undefined.

It can be easily solved by making sure that you are using the proper syntax when calling the function.

You also have to make sure that the function is properly defined and accessible.

By following the guide above, you will surely solve this error quickly.

That is all for this tutorial, IT source coders!

We hope you have learned a lot from this. Have fun coding.

Thank you for reading! 😊