testing: feature request: mechanism to disable test caching for specific unit tests

[dudleycodes]

What version of Go are you using (go version)?

$ go version
go version go1.13.1 darwin/amd64

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/{name}/Library/Caches/go-build"
GOENV="/Users/{name}/Library/Application Support/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users/{name}/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/Cellar/go/1.13.1/libexec"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/Cellar/go/1.13.1/libexec/pkg/tool/darwin_amd64"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/rv/cjpwdbp50p573x7q0ggx9bjc0000gp/T/go-build190894529=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

I'm writing integration tests using the testing package that are triggered via build tags; e.g.:

// +build integration

package myservice

func Test123(t *testing.T) {
        ....
}

Due to the nature of the integration tests their results should never be cached as the systems they are integrating against are always changing.

What did you expect to see?

A mechanism to disable caching for specific test functions.

What did you see instead?

Mechanisms for either clearing the cache for all tests or disabling the cache for all test.

Workaround

Can currently workaround this issues by running tests twice:

1. Run all unit tests, which the cache should be maintained for, via go test ./...
2. Run integration test by using the build tag and combining with -count=1 -run=....

This workaround requires that all tests that should never be cached have a regex pattern that be be used; forcing all these test to include the phrase NoCache or something else. These tests would also still need to be protected by requiring a build tag to prevent them from being run in step 1.

Proposal

Add a NoCache() method to the testing.T struct that would disable the specific method from being cached.

// +build integration

package myservice

func Test123(t *testing.T) {
        t.NoCache()
        ....
}

[ALTree]

Thanks for the request. This is a dup of #23799.

[ianlancetaylor]

Thanks. Closing as a dup. Please comment over on #23799.