test: fixture workflow to make test functions concise

Makefile

@@ -2,3 +2,6 @@ default:	test
 
 test:	*.go
 	GOPATH=~/as/logyard go test -v
+
+fmt:
+	go fmt .

tail.go

@@ -1,8 +1,8 @@
 package tail
 
 import (
-	"fmt"
 	"bufio"
+	"fmt"
 	"io"
 	"launchpad.net/tomb"
 	"log"

tail_test.go

@@ -1,11 +1,11 @@
 package tail
 
 import (
+	_ "fmt"
+	"io/ioutil"
+	"os"
 	"testing"
 	"time"
-	"os"
-	"io/ioutil"
-	_ "fmt"
 )
 
 func init() {
@@ -35,55 +35,70 @@ func TestMissingFile(t *testing.T) {
 }
 
 func TestLocationMinusOne(t *testing.T) {
-	fix := NewFixture("simple")
-	err := ioutil.WriteFile(fix.path + "/test.txt", []byte("hello\nworld\n"), 0777)
-	if err != nil {
-		t.Error(err)
-	}
-	tail, err := TailFile(fix.path + "/test.txt", Config{Follow: true, Location: -1})
-	if err != nil {
-		t.Error(err)
-	}
-	go CompareTailWithLines(t, tail, []string{"hello", "world"})
+	fix := NewFixture("simple", t)
+	fix.CreateFile("test.txt", "hello\nworld\n")
+	tail := fix.StartTail("test.txt", Config{Follow: true, Location: -1})
+	go fix.VerifyTail(tail, []string{"hello", "world"})
 
-	// delete after 1 second, to give tail sufficient time to read all lines.
-	<-time.After(1 * time.Second)
-	err = os.Remove(fix.path + "/test.txt")
-	if err != nil {
-		t.Error(err)
-	}
+	// Delete after a reasonable delay, to give tail sufficient time
+	// to read all lines.
+	<-time.After(250 * time.Millisecond)
+	fix.RemoveFile("test.txt")
 	tail.Stop()
 }
 
 type Fixture struct {
 	Name string
 	path string
+	t    *testing.T
 }
 
-func NewFixture(name string) Fixture {
-	fix := Fixture{name, ".test/" + name}
-	os.MkdirAll(fix.path, os.ModeTemporary | 0700)
+func NewFixture(name string, t *testing.T) Fixture {
+	fix := Fixture{name, ".test/" + name, t}
+	err := os.MkdirAll(fix.path, os.ModeTemporary|0700)
+	if err != nil {
+		t.Fatal(err)
+	}
 	return fix
 }
 
-func CompareTailWithLines(t *testing.T, tail *Tail, lines []string) {
+func (fix Fixture) CreateFile(name string, contents string) {
+	err := ioutil.WriteFile(fix.path+"/"+name, []byte(contents), 0777)
+	if err != nil {
+		fix.t.Fatal(err)
+	}
+}
+
+func (fix Fixture) RemoveFile(name string) {
+	err := os.Remove(fix.path + "/" + name)
+	if err != nil {
+		fix.t.Fatal(err)
+	}
+}
+
+func (fix Fixture) StartTail(name string, config Config) *Tail {
+	tail, err := TailFile(fix.path+"/"+name, config)
+	if err != nil {
+		fix.t.Fatal(err)
+	}
+	return tail
+}
+
+func (fix Fixture) VerifyTail(tail *Tail, lines []string) {
 	for _, line := range lines {
 		tailedLine, ok := <-tail.Lines
 		if !ok {
-			t.Error("insufficient lines from tail")
-			return
+			fix.t.Fatal("insufficient lines from tail")
 		}
 		if tailedLine == nil {
-			t.Errorf("tail.Lines returned nil; not possible")
-			return
+			fix.t.Fatalf("tail.Lines returned nil; not possible")
 		}
 		if tailedLine.Text != line {
-			t.Errorf("mismatch; %s != %s", tailedLine.Text, line)
-			return
+			fix.t.Fatalf("mismatch; %s != %s", tailedLine.Text, line)
 		}
 	}
 	line, ok := <-tail.Lines
 	if ok {
-		t.Errorf("more content from tail: %s", line.Text)
+		fix.t.Fatalf("more content from tail: %s", line.Text)
 	}
 }