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‎.editorconfig

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[*.go]
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tab_width = 4
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max_line_length = 80

‎.github/workflows/main.yml

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name: main
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on: [push]
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jobs:
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op:
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runs-on: ${{ matrix.os }}
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strategy:
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matrix:
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os: [ubuntu-latest, macos-latest, windows-latest]
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go: [stable, oldstable]
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steps:
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- uses: actions/checkout@v4
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- uses: actions/setup-go@v5
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with:
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go-version: ${{ matrix.go }}
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check-latest: true
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- run: go install lesiw.io/op@latest
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- run: op

‎.golangci.yml

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linters:
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enable:
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- errcheck
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- errname
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- gocheckcompilerdirectives
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- gocyclo
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- godot
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- lll
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- makezero
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- revive
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- unparam
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- unused
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linters-settings:
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gocyclo:
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min-complexity: 15
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lll:
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tab-width: 4
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line-length: 79
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issues:
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exclude-rules:
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- linters:
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- errcheck
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source: "defer "
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exclude-use-default: false
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exclude:
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- Error return value of .((os\.)?std(out|err)\..*|.*Close|.*Flush|os\.Remove(All)?|.*printf?|os\.(Un)?Setenv). is not checked
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- func name will be used as test\.Test.* by other packages, and that stutters; consider calling this
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- (possible misuse of unsafe.Pointer|should have signature)
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- ineffective break statement. Did you mean to break out of the outer loop
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- Use of unsafe calls should be audited
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- Subprocess launch(ed with variable|ing should be audited)
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- G104
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- (Expect directory permissions to be 0750 or less|Expect file permissions to be 0600 or less)
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- Potential file inclusion via variable

‎.ops/.uuid

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1840c247-60c6-473b-8196-7b3a319f2324

‎.ops/go.mod

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module ops.localhost
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go 1.24.0
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require (
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labs.lesiw.io/ops v0.0.0-20250220031357-f371eedb0d12
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lesiw.io/ops v0.14.0
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)
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require (
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golang.org/x/crypto v0.33.0 // indirect
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golang.org/x/sync v0.11.0 // indirect
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lesiw.io/clerk v0.2.0 // indirect
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lesiw.io/cmdio v0.9.0 // indirect
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lesiw.io/cmdio/x/busybox v0.1.0 // indirect
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lesiw.io/defers v0.9.0 // indirect
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lesiw.io/flag v0.7.0 // indirect
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lesiw.io/prefix v0.1.0 // indirect
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)

‎.ops/go.sum

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github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
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github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
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golang.org/x/crypto v0.33.0 h1:IOBPskki6Lysi0lo9qQvbxiQ+FvsCC/YWOecCHAixus=
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golang.org/x/crypto v0.33.0/go.mod h1:bVdXmD7IV/4GdElGPozy6U7lWdRXA4qyRVGJV57uQ5M=
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golang.org/x/sync v0.11.0 h1:GGz8+XQP4FvTTrjZPzNKTMFtSXH80RAzG+5ghFPgK9w=
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golang.org/x/sync v0.11.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
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golang.org/x/sys v0.30.0 h1:QjkSwP/36a20jFYWkSue1YwXzLmsV5Gfq7Eiy72C1uc=
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golang.org/x/sys v0.30.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
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golang.org/x/term v0.29.0 h1:L6pJp37ocefwRRtYPKSWOWzOtWSxVajvz2ldH/xi3iU=
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golang.org/x/term v0.29.0/go.mod h1:6bl4lRlvVuDgSf3179VpIxBF0o10JUpXWOnI7nErv7s=
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gotest.tools/v3 v3.5.1 h1:EENdUnS3pdur5nybKYIh2Vfgc8IUNBjxDPSjtiJcOzU=
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gotest.tools/v3 v3.5.1/go.mod h1:isy3WKz7GK6uNw/sbHzfKBLvlvXwUyV06n6brMxxopU=
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labs.lesiw.io/ops v0.0.0-20250220031357-f371eedb0d12 h1:LTlhmr7P3ND6tyiJtOo5acNRrv70IYFdDe0hdVq0Opk=
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labs.lesiw.io/ops v0.0.0-20250220031357-f371eedb0d12/go.mod h1:C9Jk4AQOr5M0NGk2oTkNJwGdX7mISjG+tebn0n3SyII=
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lesiw.io/clerk v0.2.0 h1:Rcq19dHx9TRk4Rkpm9Sw/KGySUxrNmPhrcmU2EQhBYo=
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lesiw.io/clerk v0.2.0/go.mod h1:WMyvgTe+3Eob36b6KX86MOaxaeNMvv/HZTSsf2Dedhg=
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lesiw.io/cmdio v0.9.0 h1:m4soyeXn9Xuelt6UHr4+piFLheb/L4lveJJ8p6PguGE=
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lesiw.io/cmdio v0.9.0/go.mod h1:RRxYqFsLgx3JpElt244AGmRdeFGnc/6fbh3fFgcNvnk=
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lesiw.io/cmdio/x/busybox v0.1.0 h1:e1G1JJttIcwpGuUki7oLQTx7Ve6BWExe2Cs4aw0kExM=
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lesiw.io/cmdio/x/busybox v0.1.0/go.mod h1:PkwZVzE2tTrNI4BNOgiz595SwwF8BAbvI9LSz1P5GJY=
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lesiw.io/defers v0.9.0 h1:Sg7RYbhxfHhXMHclO65MJ4oRbyhfSBSeHQw4YjLr6n0=
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lesiw.io/defers v0.9.0/go.mod h1:AP09yGFHxL5vmTVJxkPL33N1hWI4OzHwTEOzilbDZU4=
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lesiw.io/flag v0.7.0 h1:+8rTdoplDMBhOSKok5eKP6ZuLLPTodkDABRY7jfX5JU=
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lesiw.io/flag v0.7.0/go.mod h1:bJx6Hir8MAXkNiO6BbrvhwZuaJF4rQWthQ7pc1DlWZY=
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lesiw.io/ops v0.14.0 h1:WTdNxlqL2HjDgpDd5VqoaQwKOqvu1CeR1Wi1wk6wJ0E=
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lesiw.io/ops v0.14.0/go.mod h1:onq4+252Tz6+DzGMtUiibOm7+KJW+ty8v5OBJ91Yb7M=
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lesiw.io/prefix v0.1.0 h1:2Ors12avAiADgMbsQHh27wQmoSI+4aZSW2uTBdDmIZg=
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lesiw.io/prefix v0.1.0/go.mod h1:yrUaJpvikavNodwcL64crLnSf3t1NWeNi/vNu5hUi2Y=

‎.ops/ops.go

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// op is the command line for project operations.
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package main
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import (
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"os"
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"labs.lesiw.io/ops/goapp"
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"lesiw.io/ops"
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)
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// Ops is the set of operations for this project.
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type Ops struct{ goapp.Ops }
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func main() {
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goapp.Name = "testdetect"
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if len(os.Args) < 2 {
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os.Args = append(os.Args, "build")
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}
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ops.Handle(Ops{})
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}

‎LICENSE

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The MIT License (MIT)
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Copyright (c) 2025 Chris Lesiw
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Permission is hereby granted, free of charge, to any person obtaining
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a copy of this software and associated documentation files (the
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"Software"), to deal in the Software without restriction, including
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without limitation the rights to use, copy, modify, merge, publish,
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distribute, sublicense, and/or sell copies of the Software, and to
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permit persons to whom the Software is furnished to do so, subject to
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the following conditions:
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The above copyright notice and this permission notice shall be
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included in all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
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CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
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TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
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SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

‎README.md

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# testdetect
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Despite [many](https://github.com/golang/go/issues/12120),
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[many](https://github.com/golang/go/issues/14668),
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[many](https://github.com/golang/go/issues/21360),
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[many](https://github.com/golang/go/issues/52600),
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[many](https://github.com/golang/go/issues/60737),
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[many](https://github.com/golang/go/issues/60772),
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[many](https://github.com/golang/go/issues/64356)
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requests and proposals for a compile-time constraint to strip out test-time
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specific code, Go still does not have a `test` build tag.
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[`testing.Testing()`](https://pkg.go.dev/testing#Testing) was added in Go 1.21
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but is sadly not constant, meaning any code gated behind it will still be
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present in a release binary.
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`testdetect` generates a package-local `testingDetector` type with a single
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method, `Testing()`. While not a true constant, this method is "constant
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enough" that most Go compilers will optimize test related branches out of the
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finished binary. In this way, it's the closest thing to an `#ifdef TEST` as we
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can get.
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## Usage
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Run this in your Go package's directory.
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```sh
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go run lesiw.io/testdetect@latest
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```
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Alternatively, include it in your Go code as a `go generate` directive.
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```go
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//go:generate go run lesiw.io/testdetect@latest
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```
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This produces two files, `testing_detector.go` and `testing_detector_test.go`.
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Write your test-specific code behind a `(testingDetector).Testing()` check.
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```go file=main.go
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package main
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var t testingDetector
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func main() {
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if t.Testing() {
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println("t.Testing()=true")
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} else {
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println("t.Testing()=false")
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}
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println("Hello world!")
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}
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```
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## Caveats and details
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As of February 2025, checking for `Testing()` in this way correctly strips
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test-related branches from Go programs compiled by `gc` (the primary Go
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implementation) and `tinygo`. It does not work for `gccgo`.
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Technically, this is reliant on implementation details of each of these
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compilers, which are not defined in the Go specification and are subject to
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change. That said, I find it unlikely that dead code elimination will regress
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to the point where these branches are no longer optimized out, and even when
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building binaries using versions of the Go toolchain from years ago,
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removal of the `if t.Testing() == true` branches has proven consistent.
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This generator generates a number of superfluous lines to avoid contributing
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negatively to code coverage or tripping up popular linting tools. Since the
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entire point of this package is to provide a testing tool that hopefully helps
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you improve your own code coverage, generating additional uncovered lines is
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considered a bug.
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It is theoretically possible to tamper with the value of `t.Testing()`. To
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validate that this does not happen, an `init()` function has been added to
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`testing_detector.go `that checks to ensure the value of `t.Testing()` is
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always equal to `testing.Testing()`, whose value is set at compile time. In
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the unlikely event someone were to add the contents of the
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`testing_detector_test.go` file into a large codebase, the program would detect
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the discrepancy and panic on initialization.
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The actual mechanism behind `testingDetector`'s differing behavior between
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test and non-test binaries is well-defined in the
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[Go spec](https://go.dev/ref/spec). Specifically, it (ab)uses
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[selector rules](https://go.dev/ref/spec#Selectors), adding a new method to
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`testingDetector` type that is only present in the `_test.go` file. So while
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implementations of dead code elimination may differ from compiler to compiler,
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this code is perfectly valid by Go spec rules and will never fail to compile.
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## A hypothetical better future
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I've built this in the hopes that it will someday be retired.
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All of this package's complexity could be reduced by treating `_test.go` files
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the same as any other build constraint and exposing a `test` build tag.
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```go filename=undertest_false.go
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//go:build !test
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// +build !test
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package main
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const undertest = false
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```
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```go filename=undertest_true.go
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//go:build test
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// +build test
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package main
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const undertest = true
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```
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Being a constant declaration, this does not harm code coverage metrics and is
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impossible to tamper with: a constant can only be declared once, so declaring
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it a second time elsewhere in the code would be a compiler error.
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I am personally of the opinion that this is simpler, more understandable, less
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surprising, and a simple `if false == true` check is highly likely to be
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optimized out by any current or future Go compiler.

‎clerk.sum

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.editorconfig 3632ddbf531e998e5990a3d4e88b547fea86dd00
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.github/workflows/main.yml 62efcdd9a8f00f489693e4f0f916429822dc311f
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.golangci.yml 024a396bbe13b652e1c0c871bacf066672a5b18a

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