testdata/testing.go: update so it can be run with go 1.16 for comparison

testdata/testing.go

@@ -3,6 +3,8 @@ package main
 // TODO: also test the verbose version.
 
 import (
+	"errors"
+	"io"
 	"testing"
 )
 
@@ -33,14 +35,26 @@ var benchmarks = []testing.InternalBenchmark{}
 
 var examples = []testing.InternalExample{}
 
+var errMain = errors.New("testing: unexpected use of func Main")
+
+// matchStringOnly is part of upstream, and is used below to provide a dummy deps to pass to MainStart
+// so it can be run with go (tested with go 1.16) to provide a baseline for the regression test.
+// See c56cc9b3b57276.  Unfortunately, testdeps is internal, so we can't just use &testdeps.TestDeps{}.
+type matchStringOnly func(pat, str string) (bool, error)
+
+func (f matchStringOnly) MatchString(pat, str string) (bool, error)   { return f(pat, str) }
+func (f matchStringOnly) StartCPUProfile(w io.Writer) error           { return errMain }
+func (f matchStringOnly) StopCPUProfile()                             {}
+func (f matchStringOnly) WriteProfileTo(string, io.Writer, int) error { return errMain }
+func (f matchStringOnly) ImportPath() string                          { return "" }
+func (f matchStringOnly) StartTestLog(io.Writer)                      {}
+func (f matchStringOnly) StopTestLog() error                          { return errMain }
+func (f matchStringOnly) SetPanicOnExit0(bool)                        {}
+
 func main() {
-	m := testing.MainStart(testdeps{}, tests, benchmarks, examples)
+	m := testing.MainStart(matchStringOnly(nil), tests, benchmarks, examples)
 	exitcode := m.Run()
 	if exitcode != 0 {
 		println("exitcode:", exitcode)
 	}
 }
-
-type testdeps struct{}
-
-func (testdeps) MatchString(pat, str string) (bool, error) { return true, nil }