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https://github.com/agnivade/wasmbrowsertest

Run WASM tests inside your browser
https://github.com/agnivade/wasmbrowsertest

browser chromedp exec golang runtime testing wasm

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Run WASM tests inside your browser

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# wasmbrowsertest ![Build Status](https://github.com/agnivade/wasmbrowsertest/actions/workflows/ci.yml/badge.svg?branch=master)



Run Go wasm tests easily in your browser.



If you have a codebase targeting the wasm platform, chances are you would want to test your code in a browser. Currently, that process is a bit cumbersome:

- The test needs to be compiled to a wasm file.

- Then loaded into an HTML file along with the wasm_exec.js.

- And finally, this needs to be served with a static file server and then loaded in the browser.



This tool automates all of that. So you just have to type `GOOS=js GOARCH=wasm go test`, and it automatically executes the tests inside a browser !



## Quickstart



- `go install github.com/agnivade/wasmbrowsertest@latest`. This will place the binary in $GOPATH/bin, or $GOBIN, if that has a different value.

- Rename the binary to `go_js_wasm_exec`.

- Add $GOBIN to $PATH if it is not already done.

- Run tests as usual: `GOOS=js GOARCH=wasm go test`.

- You can also take a cpu profile. Set the `-cpuprofile` flag for that.



## Ok, but how does the magic work ?



`go test` allows invocation of a different binary to run a test. `go help test` has a line: 



```

-exec xprog

	    Run the test binary using xprog. The behavior is the same as

	    in 'go run'. See 'go help run' for details.

```



And `go help run` says:



```

By default, 'go run' runs the compiled binary directly: 'a.out arguments...'.

If the -exec flag is given, 'go run' invokes the binary using xprog:

	'xprog a.out arguments...'.

If the -exec flag is not given, GOOS or GOARCH is different from the system

default, and a program named go_$GOOS_$GOARCH_exec can be found

on the current search path, 'go run' invokes the binary using that program,

for example 'go_nacl_386_exec a.out arguments...'. This allows execution of

cross-compiled programs when a simulator or other execution method is

available.

```



So essentially, there are 2 ways:

- Either have a binary with the name of `go_js_wasm_exec` in your $PATH.

- Or set the `-exec` flag in your tests.



Use whatever works for you.



### How is a CPU profile taken ?



A CPU profile is run during the duration of the test, and then converted to the pprof format so that it can be natively analyzed with the Go toolchain.



### Can I run something which is not a test ?



Yep. `GOOS=js GOARCH=wasm go run main.go` also works. If you want to actually see the application running in the browser, set the `WASM_HEADLESS` variable to `off` like so `WASM_HEADLESS=off GOOS=js GOARCH=wasm go run main.go`.



### Can I use this inside Travis ?



Sure.



Add these lines to your `.travis.yml`



```

addons:

  chrome: stable



install:

- go install github.com/agnivade/wasmbrowsertest@latest

- mv $GOPATH/bin/wasmbrowsertest $GOPATH/bin/go_js_wasm_exec

- export PATH=$GOPATH/bin:$PATH

```



Now, just setting `GOOS=js GOARCH=wasm` will run your tests using `wasmbrowsertest`. For other CI environments, you have to do something similar.



### Can I use this inside Github Action?



Sure.



Add these lines to your `.github/workflows/ci.yml`



PS: adjust the go version you need in go-version section



```

on: [push, pull_request]

name: Unit Test

jobs:

  test:

    strategy:

      matrix:

        go-version: [1.xx.x]

        os: [ubuntu-latest]

    runs-on: ${{ matrix.os }}

    steps:

    - name: Install Go

      uses: actions/setup-go@v2

      with:

        go-version: ${{ matrix.go-version }}

    - name: Install chrome

      uses: browser-actions/setup-chrome@latest

    - name: Install dep

      run: go install github.com/agnivade/wasmbrowsertest@latest

    - name: Setup wasmexec

      run: mv $(go env GOPATH)/bin/wasmbrowsertest $(go env GOPATH)/bin/go_js_wasm_exec

    - name: Checkout code

      uses: actions/checkout@v2

```



### What sorts of browsers are supported ?



This tool uses the [ChromeDP](https://chromedevtools.github.io/devtools-protocol/) protocol to run the tests inside a Chrome browser. So Chrome or any blink-based browser will work.



### Why not firefox ?



Great question. The initial idea was to use a Selenium API and drive any browser to run the tests. But unfortunately, geckodriver does not support the ability to capture console logs - https://github.com/mozilla/geckodriver/issues/284. Hence, the shift to use the ChromeDP protocol circumvents the need to have any external driver binary and just have a browser installed in the machine.



### A tip on coverage data using go 1.20 or later:



Code coverage changes introduced in go 1.20 produce multiple 

[coverage data files](https://go.dev/testing/coverage/#working) in binary format.



In wasmbrowsertest, file system operations for coverage files occur via HTTP API calls.

  

Prefer using `-test.gocoverdir=/path/to/coverage` instead of `-test.coverprofile=coverage.out` 

when coverage data is needed. This will prevent http api calls that would read all the coverage data 

files and write the larger `coverage.out` file. 



In a subsequent step, use `go tool covdata -i /path/to/coverage -o coverage.out` or similar to process coverage 

data files into the desired output format. An additional benefit is that multiple test coverage runs that write 

their data to the same coverage directory can be merged together with this command.



## Errors



### `total length of command line and environment variables exceeds limit`



If the error `total length of command line and environment variables exceeds limit` appears, then

the current environment variables' total size has exceeded the maximum when executing Go Wasm binaries.



To resolve this issue, install `cleanenv` and use it to prefix your command.



For example, if these commands are used:

```bash

export GOOS=js GOARCH=wasm

go test -cover ./...

```

The new commands should be the following:

```bash

go install github.com/agnivade/wasmbrowsertest/cmd/cleanenv@latest



export GOOS=js GOARCH=wasm

cleanenv -remove-prefix GITHUB_ -- go test -cover ./...

```



The `cleanenv` command above removes all environment variables prefixed with `GITHUB_` before running the command after the `--`.

The `-remove-prefix` flag can be repeated multiple times to remove even more environment variables.