Tutorial: LIT and FileCheck¶

This tutorial assumes that you have installed lit and filecheck and have them available in your PATH:

$ filecheck
/usr/local/bin/filecheck
<check-file> not specified

$ lit
...
lit: error: No inputs specified

Minimal example¶

When writing LIT/FileCheck tests it is common, but not required, to combine LIT’s RUN commands and FileCheck’s CHECK assertions in a single file.

Let’s create a file minimal.itest with the following contents

RUN: echo "Hello world" | filecheck %s
CHECK: Hello world

LIT expects a config file in a directory from which it is run. Let’s create a minimal one called lit.cfg:

import lit.formats
config.test_format = lit.formats.ShTest("0")

Now we can run lit:

lit minimal.itest

-- Testing: 1 tests, single process --
PASS: <unnamed> :: test.itest (1 of 1)
Testing Time: 0.10s
  Expected Passes    : 1

Example: testing output of C program¶

Passing test¶

Test file 01-pass.c:

/**
RUN: clang %s -o %S/hello-world && %S/hello-world | filecheck %s
CHECK: Hello world
 */

#include <stdio.h>
int main() {
  printf("Hello world\n");
  return 0;
}

Command:

$ lit 01-pass.c

Output:

-- Testing: 1 tests, single process --
PASS: <unnamed> :: 01-pass.c (1 of 1)
Testing Time: 0.10s
  Expected Passes    : 1

Failing test¶

Test file 02-fail.c:

/**
RUN: clang %s -o %S/hello-world && %S/hello-world | filecheck %s
CHECK: Wrong line
 */

#include <stdio.h>
int main() {
  printf("Hello world\n");
  return 0;
}