testhelper.mod

Some useful functions and types to simplify and improve testing.

Several of these are intended to be used as unnamed members of a testcase struct. The testcase idiom is a table-driven testing scheme where you first define a slice of structs with the struct holding the parameters to the test and the expected results. Then you iterate over the individual test cases running the code you are testing and compare the results with the expected results.

the testhelper.ID type

This is intended to be used as an unnamed member of a testcase struct. Then for each testcase instance you initialise the value using the constructor:

testhelper.MkID("...")

This has the advantage over a simple string that the constructor records the filename and linenumber where MkID(...) was called which makes it easier to find the precise test that is failing. It can be used to give a useful description of the test case through the IDStr() method.

A struct with this embedded will satisfy the testhelper.TestCase interface.

the testhelper.ExpErr type

This is intended to be used as an unnamed member of a testcase struct (though if you want to check more than one error condition you can add more). It is initialised using the constructor:

testhelper.MkErr("part of the error message", "some more", "etc")

The default value expresses that no error is expected. If it is initialised a non-nil error is expected and the strings passed are expected to be found in the error message.

A struct with this embedded will satisfy the testhelper.TestErr interface and if the struct also has a testhelper.ID embedded then it will satisfy the testhelper.TestCaseWithErr interface. This can then be passed to testhelper.CheckExpErr which will report a test error if the error is not as expected.

the testhelper.ExpPanic type

This is intended to be used as an unnamed member of a testcase struct (though if you want to check more than one panic you can add more). It is initialised using the constructor:

testhelper.MkExpPanic("part of the panic message", "some more", "etc")

The default value expresses that no panic is expected. If it is initialised a panic is expected and the strings passed are expected to be found in the panic value (which is expected to be a string).

A struct with this embedded will satisfy the testhelper.TestPanic interface and if the struct also has a testhelper.ID embedded then it will satisfy the testhelper.TestCaseWithPanic interface. This can then be passed to testhelper.CheckExpPanic which will report a test error if the panic is not as expected.

the StringSliceDiff func

This takes a pair of string slices and returns true if they differ, false otherwise.

the ShouldContain func

This takes a string and a slice of strings and reports test errors for each string in the slice that isn't in the string. If any strings are missing it will return true, otherwise false.

the CheckAgainstGoldenFile func

This checks that the passed slice of bytes is the same as the value read from the golden file. You can pass a flag to get the file created initially and to update it when there has been a desired change in the output being checked. It returns true if the passed bytes match the contents of the golden file, false otherwise.

When updating golden files the original contents are recorded in a new file with the same name plus a suffix of .orig. These can then be compared against the original to see the changes. It is recommended that you add a line to a .gitignore file (if you're using git) to make sure that you don't accidentally save these files.