Improved error messages

file.go

@@ -3,16 +3,21 @@ package assert
 import (
 	"runtime/debug"
 	"strings"
-	"testing"
 )
 
 // file returns the first line containing "_test.go" in the debug stack.
-func file(t testing.TB) string {
+func file() string {
 	stack := string(debug.Stack())
 	lines := strings.Split(stack, "\n")
 
 	for _, line := range lines {
 		if strings.Contains(line, "_test.go") {
+			space := strings.LastIndex(line, " ")
+
+			if space != -1 {
+				line = line[:space]
+			}
+
 			return strings.TrimSpace(line)
 		}
 	}