Added equality checks

file.go

@@ -0,0 +1,21 @@
+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 {
+	stack := string(debug.Stack())
+	lines := strings.Split(stack, "\n")
+
+	for _, line := range lines {
+		if strings.Contains(line, "_test.go") {
+			return strings.TrimSpace(line)
+		}
+	}
+
+	return ""
+}