testing: --run now allows filtering of subtests

Also fix typo in error message in sub_test.go from upstream,
and move a few members from B to common where they belonged.

Note that testdata/testing.go seems to be pushing the edge of what
the emulated cortex-m3 target can handle; using regexp in that test
causes it to fail on that target with an out of memory error.

TODO: once tinygo supports runtime.Goexit, consider just using upstream's testing directory...

testdata/testing.go

@@ -4,6 +4,7 @@ package main
 
 import (
 	"errors"
+	"flag"
 	"io"
 	"testing"
 )
@@ -26,15 +27,60 @@ func TestBar(t *testing.T) {
 	t.Log("log Bar end")
 }
 
+func TestAllLowercase(t *testing.T) {
+	names := []string {
+		"alpha",
+		"BETA",
+		"gamma",
+		"DELTA",
+	}
+
+	for _, name := range names {
+		t.Run(name, func(t *testing.T) {
+			if 'a' <= name[0] && name[0] <= 'a' {
+				t.Logf("expected lowercase name, and got one, so I'm happy")
+			} else {
+				t.Errorf("expected lowercase name, got %s", name)
+			}
+		})
+	}
+}
+
 var tests = []testing.InternalTest{
 	{"TestFoo", TestFoo},
 	{"TestBar", TestBar},
+	{"TestAllLowercase", TestAllLowercase},
 }
 
 var benchmarks = []testing.InternalBenchmark{}
 
 var examples = []testing.InternalExample{}
 
+// A fake regexp matcher that can only handle two patterns.
+// Inflexible, but saves 50KB of flash and 50KB of RAM per -size full,
+// and lets tests pass on cortex-m3.
+func fakeMatchString(pat, str string) (bool, error) {
+	if pat == ".*" {
+		return true, nil
+	}
+	if pat == "[BD]" {
+		return (str[0] == 'B' || str[0] == 'D'), nil
+	}
+	println("BUG: fakeMatchString does not grok", pat)
+	return false, nil
+}
+
+func main() {
+	testing.Init()
+	flag.Set("test.run", ".*/[BD]")
+	m := testing.MainStart(matchStringOnly(fakeMatchString /*regexp.MatchString*/), tests, benchmarks, examples)
+
+	exitcode := m.Run()
+	if exitcode != 0 {
+		println("exitcode:", exitcode)
+	}
+}
+
 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
@@ -50,11 +96,3 @@ 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(matchStringOnly(nil), tests, benchmarks, examples)
-	exitcode := m.Run()
-	if exitcode != 0 {
-		println("exitcode:", exitcode)
-	}
-}

testdata/testing.txt

@@ -12,5 +12,10 @@
         failed
         after failed
     log Bar end
+--- FAIL: TestAllLowercase (0.00s)
+    --- FAIL: TestAllLowercase/BETA (0.00s)
+        expected lowercase name, got BETA
+    --- FAIL: TestAllLowercase/DELTA (0.00s)
+        expected lowercase name, got DELTA
 FAIL
 exitcode: 1