internal/broadcasts: fix test fluke

I'm not 100% sure how this ever passed so often. range over a map is
guaranteed to be random per the language spec. Not sure if this is
different for pointers but I'd be supprised.

Well, now this is testing the right things directly at least and doesn't
depend on the order of the output.

internal/broadcasts/broadcast_test.go

@@ -3,14 +3,21 @@
 package broadcasts
 
 import (
+	"bytes"
 	"errors"
 	"fmt"
+	"io"
+	"os"
+	"strings"
+	"testing"
 )
 
-type testPrinter struct{}
+type testPrinter struct {
+	w io.Writer
+}
 
 func (tp testPrinter) Update(members []string) error {
-	fmt.Printf("test: %d\n", len(members))
+	fmt.Fprintf(tp.w, "test: %d\n", len(members))
 	return nil
 }
 
@@ -21,6 +28,8 @@ func ExampleBroadcast() {
 	defer sink.Close()
 
 	var p1, p2 testPrinter
+	p1.w = os.Stdout
+	p2.w = os.Stdout
 
 	closeSink := bcast.Register(p1)
 	defer closeSink()
@@ -39,6 +48,8 @@ func ExampleBroadcastCanceled() {
 	defer sink.Close()
 
 	var p1, p2 testPrinter
+	p1.w = os.Stdout
+	p2.w = os.Stdout
 
 	closeSink := bcast.Register(p1)
 	defer closeSink()
@@ -52,21 +63,29 @@ func ExampleBroadcastCanceled() {
 	// test: 1
 }
 
-type erroringPrinter struct{}
+type erroringPrinter struct {
+	w io.Writer
+}
 
 func (tp erroringPrinter) Update(m []string) error {
-	fmt.Printf("failed: %d\n", len(m))
+	fmt.Fprintf(tp.w, "failed: %d\n", len(m))
+	// time.Sleep(1 * time.Second)
 	return errors.New("nope")
 }
 
 func (tp erroringPrinter) Close() error { return nil }
 
-func ExampleBroadcastOneErrs() {
+func TestBroadcastOneErrs(t *testing.T) {
+	var buf = &bytes.Buffer{}
+
 	sink, bcast := NewRoomChanger()
 	defer sink.Close()
 
 	var p1 testPrinter
+	p1.w = buf
+
 	var p2 erroringPrinter
+	p2.w = buf
 
 	closeSink := bcast.Register(p1)
 	defer closeSink()
@@ -77,10 +96,26 @@ func ExampleBroadcastOneErrs() {
 
 	sink.Update([]string{"run", "2"})
 
-	// Output:
-	// test: 1
-	// failed: 1
-	// test: 2
+	output := buf.String()
+
+	expectedContains := []string{
+		"test: 1\n",
+		"failed: 1\n",
+		"test: 2\n",
+	}
+
+	for i, exp := range expectedContains {
+		if !strings.Contains(output, exp) {
+			t.Errorf("expected %d in ouput but it didn't", i+1)
+			t.Log(output)
+		}
+	}
+
+	lines := strings.Split(output, "\n")
+	if n := len(lines); n != 4 { // 3 and one empty one
+		t.Errorf("expected 4 lines of output but got %d", n)
+		t.Log(output)
+	}
 }
 
 /*