Print out the correct point of error

testing/unit/subject.go

@@ -1,5 +1,12 @@
 package unit
 
+import (
+	"bytes"
+	"fmt"
+	"runtime"
+	"strings"
+)
+
 type Subject struct {
 	assert *Assertion
 	name   string
@@ -12,8 +19,43 @@ func NewSubject(assert *Assertion) *Subject {
 	}
 }
 
+// decorate prefixes the string with the file and line of the call site
+// and inserts the final newline if needed and indentation tabs for formatting.
+func decorate(s string) string {
+	_, file, line, ok := runtime.Caller(4) // decorate + log + public function.
+	if ok {
+		// Truncate file name at last file name separator.
+		if index := strings.LastIndex(file, "/"); index >= 0 {
+			file = file[index+1:]
+		} else if index = strings.LastIndex(file, "\\"); index >= 0 {
+			file = file[index+1:]
+		}
+	} else {
+		file = "???"
+		line = 1
+	}
+	buf := new(bytes.Buffer)
+	// Every line is indented at least one tab.
+	buf.WriteString("  ")
+	fmt.Fprintf(buf, "%s:%d: ", file, line)
+	lines := strings.Split(s, "\n")
+	if l := len(lines); l > 1 && lines[l-1] == "" {
+		lines = lines[:l-1]
+	}
+	for i, line := range lines {
+		if i > 0 {
+			// Second and subsequent lines are indented an extra tab.
+			buf.WriteString("\n\t\t")
+		}
+		buf.WriteString(line)
+	}
+	buf.WriteByte('\n')
+	return buf.String()
+}
+
 func (subject *Subject) FailWithMessage(message string) {
-	subject.assert.t.Error(message)
+	fmt.Println(decorate(message))
+	subject.assert.t.Fail()
 }
 
 func (subject *Subject) Named(name string) {