testing: finish implementation of subtests

API not exposed yet.

Change-Id: Iaba0adc0fa1ae8075e6b56796f99ee8db9177a78
Reviewed-on: https://go-review.googlesource.com/18896
Reviewed-by: Russ Cox <rsc@golang.org>

src/testing/sub_test.go

@@ -5,6 +5,8 @@
 package testing
 
 import (
+	"io/ioutil"
+	"sync/atomic"
 	"time"
 )
 
@@ -104,6 +106,229 @@ func TestTestContext(t *T) {
 	}
 }
 
+// TODO: remove this stub when API is exposed
+func (t *T) Run(name string, f func(t *T)) bool { return t.run(name, f) }
+
+func TestTRun(t *T) {
+	realTest := t
+	testCases := []struct {
+		desc   string
+		ok     bool
+		maxPar int
+		f      func(*T)
+	}{{
+		desc:   "failnow skips future sequential and parallel tests at same level",
+		ok:     false,
+		maxPar: 1,
+		f: func(t *T) {
+			ranSeq := false
+			ranPar := false
+			t.Run("", func(t *T) {
+				t.Run("par", func(t *T) {
+					t.Parallel()
+					ranPar = true
+				})
+				t.Run("seq", func(t *T) {
+					ranSeq = true
+				})
+				t.FailNow()
+				t.Run("seq", func(t *T) {
+					realTest.Error("test must be skipped")
+				})
+				t.Run("par", func(t *T) {
+					t.Parallel()
+					realTest.Error("test must be skipped.")
+				})
+			})
+			if !ranPar {
+				realTest.Error("parallel test was not run")
+			}
+			if !ranSeq {
+				realTest.Error("sequential test was not run")
+			}
+		},
+	}, {
+		desc:   "failure in parallel test propagates upwards",
+		ok:     false,
+		maxPar: 1,
+		f: func(t *T) {
+			t.Run("", func(t *T) {
+				t.Parallel()
+				t.Run("par", func(t *T) {
+					t.Parallel()
+					t.Fail()
+				})
+			})
+		},
+	}, {
+		desc:   "use Run to locally synchronize parallelism",
+		ok:     true,
+		maxPar: 1,
+		f: func(t *T) {
+			var count uint32
+			t.Run("waitGroup", func(t *T) {
+				for i := 0; i < 4; i++ {
+					t.Run("par", func(t *T) {
+						t.Parallel()
+						atomic.AddUint32(&count, 1)
+					})
+				}
+			})
+			if count != 4 {
+				t.Errorf("count was %d; want 4", count)
+			}
+		},
+	}, {
+		desc:   "run no more than *parallel tests concurrently",
+		ok:     true,
+		maxPar: 4,
+		f: func(t *T) {
+			max := 0
+			in := make(chan int)
+			out := make(chan int)
+			ctx := t.context
+			t.Run("wait", func(t *T) {
+				t.Run("controller", func(t *T) {
+					// Verify sequential tests don't skew counts.
+					t.Run("seq1", func(t *T) {})
+					t.Run("seq2", func(t *T) {})
+					t.Run("seq3", func(t *T) {})
+					t.Parallel()
+					for i := 0; i < 80; i++ {
+						ctx.mu.Lock()
+						if ctx.running > max {
+							max = ctx.running
+						}
+						ctx.mu.Unlock()
+						<-in
+						// force a minimum to avoid a race, although it works
+						// without it.
+						if i >= ctx.maxParallel-2 { // max - this - 1
+							out <- i
+						}
+					}
+					close(out)
+				})
+				// Ensure we don't exceed the maximum even with nested parallelism.
+				for i := 0; i < 2; i++ {
+					t.Run("", func(t *T) {
+						t.Parallel()
+						for j := 0; j < 40; j++ {
+							t.Run("", func(t *T) {
+								t.Run("seq1", func(t *T) {})
+								t.Run("seq2", func(t *T) {})
+								t.Parallel()
+								in <- j
+								<-out
+							})
+						}
+					})
+				}
+			})
+			if max != ctx.maxParallel {
+				realTest.Errorf("max: got %d; want: %d", max, ctx.maxParallel)
+			}
+		},
+	}, {
+		desc: "alternate sequential and parallel",
+		// Sequential tests should partake in the counting of running threads.
+		// Otherwise, if one runs parallel subtests in sequential tests that are
+		// itself subtests of parallel tests, the counts can get askew.
+		ok:     true,
+		maxPar: 1,
+		f: func(t *T) {
+			t.Run("a", func(t *T) {
+				t.Parallel()
+				t.Run("b", func(t *T) {
+					// Sequential: ensure running count is decremented.
+					t.Run("c", func(t *T) {
+						t.Parallel()
+					})
+
+				})
+			})
+		},
+	}, {
+		desc: "alternate sequential and parallel",
+		// Sequential tests should partake in the counting of running threads.
+		// Otherwise, if one runs parallel subtests in sequential tests that are
+		// itself subtests of parallel tests, the counts can get askew.
+		ok:     true,
+		maxPar: 2,
+		f: func(t *T) {
+			for i := 0; i < 2; i++ {
+				t.Run("a", func(t *T) {
+					t.Parallel()
+					time.Sleep(time.Nanosecond)
+					for i := 0; i < 2; i++ {
+						t.Run("b", func(t *T) {
+							time.Sleep(time.Nanosecond)
+							for i := 0; i < 2; i++ {
+								t.Run("c", func(t *T) {
+									t.Parallel()
+									time.Sleep(time.Nanosecond)
+								})
+							}
+
+						})
+					}
+				})
+			}
+		},
+	}, {
+		desc:   "stress test",
+		ok:     true,
+		maxPar: 4,
+		f: func(t *T) {
+			t.Parallel()
+			for i := 0; i < 12; i++ {
+				t.Run("a", func(t *T) {
+					t.Parallel()
+					time.Sleep(time.Nanosecond)
+					for i := 0; i < 12; i++ {
+						t.Run("b", func(t *T) {
+							time.Sleep(time.Nanosecond)
+							for i := 0; i < 12; i++ {
+								t.Run("c", func(t *T) {
+									t.Parallel()
+									time.Sleep(time.Nanosecond)
+									t.Run("d1", func(t *T) {})
+									t.Run("d2", func(t *T) {})
+									t.Run("d3", func(t *T) {})
+									t.Run("d4", func(t *T) {})
+								})
+							}
+
+						})
+					}
+				})
+			}
+		},
+	}}
+	for _, tc := range testCases {
+		ctx := newTestContext(tc.maxPar)
+		root := &T{
+			common: common{
+				barrier: make(chan bool),
+				w:       ioutil.Discard,
+			},
+			context: ctx,
+		}
+		ok := root.Run(tc.desc, tc.f)
+		ctx.release()
+
+		if ok != tc.ok {
+			t.Errorf("%s:ok: got %v; want %v", tc.desc, ok, tc.ok)
+		}
+		if ok != !root.Failed() {
+			t.Errorf("%s:root failed: got %v; want %v", tc.desc, !ok, root.Failed())
+		}
+		if ctx.running != 0 || ctx.numWaiting != 0 {
+			t.Errorf("%s:running and waiting non-zero: got %d and %d", tc.desc, ctx.running, ctx.numWaiting)
+		}
+	}
+}
+
 // TODO: remove this stub when API is exposed
 func (b *B) Run(name string, f func(b *B)) bool { return b.runBench(name, f) }