Unit Testing | Golang basics
Mahdi.Kh
September 21, 2026
In this part, we get familiar with unit testing in Go and learn how to write tests for our own code.
Unit testing is the most basic kind of test for checking that code works correctly. If we have a pyramid for the different kinds of tests, unit testing sits at the bottom of that pyramid.
As we can see, unit testing sits at the lowest level of the pyramid, meaning the first kind of test you should usually write is a unit test. The pyramid's cross-section represents the amount of testing. The bottom of the pyramid is wider than its top, and it gets narrower and smaller as you go up. In most cases, the amount of unit testing is greater than all the other kinds of testing combined.
In Go, you don't need to install separate tools to write and run unit tests; using just Go's standard packages, you can write your tests and then run them with the Go command line.
Writing Your First Unit Test
Suppose we have code for summing integers, as follows, and this code is in the sum.go file:
In Go, test files have names with the _test suffix. So if our code is in the sum.go file, our tests will go in a file named sum_test.go. Every test is a function whose name starts with Test and that has a parameter of type *testing.T.
For the code above, we can write our test inside the sum_test.go file, as follows:
To run every test, we can use the go test ./… command, and to run a specific test, we can specify the test's name using -run; for example, here we can use go test -run ^TestSum$ ./..., where TestSum represents the name of the test we want.
By passing ./…, we specify that Go should search the current directory and all its subdirectories for tests, and run them if it finds any.
Running go test -run ^TestSum$ ./... runs our test, and if it passes, it shows a result like this:
We can add more tests. For example, let's have two tests: one for the case where we pass a single number to , and one for the case where we give this function several numbers as input: