Dive deep into Go 1.15 changes to testing package

The presentation materials for Go 1.15 Release Party in Japan

Transcript

1. Dive deep into
   Go 1.15 changes to
   testing package
   Go 1.15 Release Party, AUGUST 31 2020
   #go115party
   @hgsgtk Kazuki Higashiguchi
   

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2. {
   About me
   Kazuki Higashiguchi
   GitHub/Twitter: @hgsgtk
   BASE BANK, Inc.
   (BASE, Inc.)
   

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3. Go 1.15 Release Notes
   > Minor changes to the testing
   The testing.T type now has a Deadline method ...
   A TestMain function is no longer required to call
   os.Exit. ...
   The new methods T.TempDir and B.TempDir ...
   go test -v now groups output by test name, ...
   https://golang.org/doc/go1.15#testing
   

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4. Go 1.15 Release Notes
   > Minor changes to the testing
   The testing.T type now has a Deadline method ...
   A TestMain function is no longer required to call
   os.Exit. ...
   The new methods T.TempDir and B.TempDir ...
   go test -v now groups output by test name, ...
   https://golang.org/doc/go1.15#testing
   Talk contents
   

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5. 01
   A TestMain function is no longer
   required to call os.Exit
   Minor changes to the testing in 1.15
   

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6. Go 1.15 Release Notes
   > Minor changes to the library > testing
   A TestMain function is no longer
   required to call os.Exit. If a
   TestMain function returns, the test
   binary will call os.Exit with the
   value returned by m.Run.
   https://golang.org/doc/go1.15#testing
   

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7. 1.15 or later, no longer required to call os.Exit
   No need to call os.Exit()
   

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8. https://github.com/golang/go/issues/34129
   testing: TestMain should not require os.Exit #34129
   Issued at
   2019.9.26
   

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9. Common TestMain() mistakes
   $ go test -v ./...
   === RUN TestHoge
   --- FAIL: TestHoge (0.00s)
   FAIL
   ok
   github.com/hgsgtk/go-snippets/testing
   -115/mistake 0.079s
   defer os.Exit()
   

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10. Issue #34129 testing: TestMain should not require os.Exit
    https://github.com/golang/go/issues/34129
    “This mistake does happen a lot, and the testing
    package that called TestMain and prepared the
    m can certainly record the result of m.Run for
    use in its own outer os.Exit.”
    (@rsc Russ Cox)
    

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11. https://go-review.googlesource.com/c/go/+/219639
    219639: testing: do not require os.Exit in TestMain
    Major change files ...
    src/testing/testing.go
    src/cmd/go/internal/load/
    test.go
    

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12. `go test ./...` with TestMain (before 1.15)
    `go test` generate _testmain.go code.
    src/cmd/go/main.go
    main()
    src/cmd/go/internal/test/test.go
    runTest() -> builderTest()
    src/cmd/go/internal/load
    TestPackagesFor()
    -> TestPackagesAndErrors()
    -> formatTestMain()
    -> testmainTmpl
    Template code generated by `go test`
    ( _testmain.go)
    SUT
    _test.go
    TestMain
    1. Call testing.MainStart()
    src/testing/testing.go
    MainStart()
    2. Call user-defined
    TestMain
    

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13. `go test ./...` with TestMain (1.15 or later)
    Go 1.15 or later, main func in `_testmain.go` call os.Exit().
    src/cmd/go/main.go
    main()
    src/cmd/go/internal/test/test.go
    runTest() -> builderTest()
    src/cmd/go/internal/load
    TestPackagesFor()
    -> TestPackagesAndErrors()
    -> formatTestMain()
    -> testmainTmpl
    Template code generated by `go test`
    ( _testmain.go)
    SUT
    _test.go
    TestMain
    1. Call testing.MainStart()
    src/testing/testing.go
    MainStart()
    2. Call user-defined
    TestMain
    3. Call os.Exit() with
    m.Run result code
    

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14. src/testing/testing.go
    https://go-review.googlesource.com/c/go/+/219639/10/src/testing/testing.go
    m.Run records its own result in an unexported field of m.
    

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15. src/cmd/go/internal/load/test.go
    https://go-review.googlesource.com/c/go/+/219639/10/src/cmd/go/internal/load/test.go
    if TestMain(m) returns, the outer test func main harness calls os.Exit with
    that code.
    

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16. A TestMain function is no longer required to call os.Exit
    ● A TestMain function is no longer required to call os.Exit
    ● testing.M の内部変更及び、 go test で生成される main 関
    数のテンプレート修正によって実現されている
    

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17. 02 Minor changes to the testing in 1.15
    The testing.T type now has a Deadline
    method
    

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18. Go 1.15 Release Notes
    > Minor changes to the library > testing
    The testing.T type now has a
    Deadline method that reports the
    time at which the test binary will
    have exceeded its timeout.
    https://golang.org/doc/go1.15#testing
    

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19. t.Deadline()
    https://godoc.org/testing#T.Deadline
    Deadline reports the time at which the test binary will have exceeded
    the timeout specified by the -timeout flag.
    The ok result is false if the -timeout flag indicates “no timeout” (0).
    % go test -v -timeout=5s
    -run=TestDeadlineConfirm
    t.Deadline() = 2020-08-31 18:37:39.502862
    +0900 JST m=+5.000488349, timeout set = true
    $ go test -v -timeout=0
    -run=TestDeadlineConfirm
    t.Deadline() = 0001-01-01 00:00:00 +0000
    UTC, timeout set = false
    

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20. https://github.com/golang/go/issues/28135
    testing: add (*T).Deadline #28135
    Issued at
    Oct 11, 2018
    

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21. https://go-review.googlesource.com/c/go/+/202758/
    202758: testing: testing: add (*T).Deadline method for test timeout
    Major change files ...
    src/testing/testing.go
    

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22. Inside src/testing/testing.go
    ※ 今回の変更に関連するものだけ抜粋しています
    testing.M.Run()
    runTests()
    testing.M.startAlarm()
    testing.T.Run()
    testing.T.Deadline()
    …..
    

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23. src/testing/testing.go
    https://golang.org/src/testing/testing.go#L630
    New field ‘deadline’
    in testContext
    New method T.Deadline()
    testing.T has
    *testContext
    

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24. src/testing/testing.go
    https://go-review.googlesource.com/c/go/+/202758/8/src/testing/testing.go
    t.Deadline() added in testing.go
    m.Run() call it.
    Pass arg to runTests()
    

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25. src/testing/testing.go
    https://go-review.googlesource.com/c/go/+/202758/8/src/testing/testing.go
    runTests() set deadline to testContext.deadline
    

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26. The testing.T type now has a Deadline method
    ● A new method t.Deadline
    ● It is realized by adding `deadline` field in testContext in
    testing.T
    

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27. Congrats Go 1.15 !!
    

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