https://github.com/rillig/gobco

Measure branch coverage of golang tests
https://github.com/rillig/gobco

coverage coverage-testing go golang

Last synced: about 14 hours ago
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Measure branch coverage of golang tests

• Host: GitHub
• URL: https://github.com/rillig/gobco
• Owner: rillig
• License: bsd-2-clause
• Created: 2018-11-22T06:46:06.000Z (about 6 years ago)
• Default Branch: master
• Last Pushed: 2024-09-24T20:53:09.000Z (4 months ago)
• Last Synced: 2025-01-01T09:07:01.622Z (8 days ago)
• Topics: coverage, coverage-testing, go, golang
• Language: Go
• Homepage:
• Size: 565 KB
• Stars: 73
• Watchers: 3
• Forks: 13
• Open Issues: 6
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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# GOBCO - Golang Branch Coverage

Gobco measures condition coverage of Go code.

Gobco is intended to be used in addition to `go test -cover`.

For example, gobco does not detect functions or methods that are completely

unused, it only notices them if they contain any conditions or branches.

Gobco also doesn't cover `select` statements.

## Installation

With go1.17 or later:

```text

$ go install github.com/rillig/gobco@latest

```

With go1.16:

```text

$ go get github.com/rillig/gobco

```

Older go releases are not supported.

## Usage

To run gobco on a single package, run it in the package directory:

~~~text

$ gobco

~~~

The output typically looks like the following example, taken from package

[github.com/rillig/pkglint](https://github.com/rillig/pkglint):

```text

ok  	github.com/rillig/pkglint/v23	29.648s

Condition coverage: 8720/8840

...

changes.go:171:61: condition "n == 6" was 12 times true but never false

distinfo.go:268:8: condition "alg == \"SHA1\"" was 16 times false but never true

distinfo.go:322:13: condition "remainingHashes[0].algorithm == alg" was 8 times true but never false

...

mkcondsimplifier.go:141:31: condition "p[2] == p[1]-'A'+'a'" was 26 times true but never false

...

vartypecheck.go:1027:11: condition "len(invalid) > 1" was once false but never true

vartypecheck.go:1628:42: condition "cv.MkLines.pkg != nil" was 8 times true but never false

vartypecheck.go:1630:6: condition "distname.IsConstant()" was 8 times true but never false

```

## Adding custom test conditions

If you want to ensure that the tests cover a certain condition in your code,

you can insert the desired condition into the code

and assign it to the underscore:

~~~go

func square(x int) int {

    _ = x > 50

    _ = x == 0

    _ = x < 0

    return x * x

}

~~~

The compiler will see that these conditions are side-effect-free and will thus

optimize them away, so there is no runtime overhead.

Gobco only inserts its coverage code around expressions that are syntactically

recognizable as boolean expressions, such as comparisons, '&&', '||', '!'.

When a boolean expression is merely passed around, there is no branch 

involved, thus nothing to do for branch coverage.