Greencently

Do you usually run your tests before you commit, to check your work?

Do your tests also get run by a pre-commit hook?

This is helpful in the worst case -- the pre-commit hook has your back when you forget -- but in the typical case it's harmful:

• Disrupts flow
• Doubles cost
• Adds no marginal benefit
• Discourages frequent small well-tested commits
• Engenders learned helplessness

We can fix this.

Setup for JUnit 5

1. Update build.gradle.kts:

dependencies {
    testRuntimeOnly("com.schmonz:junit-greencently:CHECK_ABOVE_FOR_VERSION")
}
tasks.withType<Test> {
    jvmArgs("-Djunit.jupiter.extensions.autodetection.enabled=true")
    maxParallelForks = 1  // see issue #4
}

2. Run all tests in project
3. If green, observe top-level timestamp file .when-all-tests-were-green-junit5
4. Append to top-level .gitignore: *when-all-tests-were-green*
5. Observe git status not showing timestamp file
6. In pre-commit hook, inspect file modification time. Example:

#!/bin/sh
all_tests_were_recently_green() {
    too_many_seconds_ago=$1
    thenstamp=$(date -r .when-all-tests-were-green-junit5 '+%s' 2>/dev/null || echo 0)
    nowstamp=$(date '+%s')
    secondsago=$(expr ${nowstamp} - ${thenstamp})
    [ ${secondsago} -lt ${too_many_seconds_ago} ]
}
if all_tests_were_recently_green 30; then
    ./gradlew clean build -x test
else
    ./gradlew clean build
fi

More information

See the Greencently webpage.