add integration tests to validate piping to the CLI

integrations/execute.js

@@ -21,9 +21,14 @@ module.exports = function $(command, options = {}) {
   let abortController = new AbortController()
   let cwd = resolveToolRoot()
 
-  let args = command.split(' ')
-  command = args.shift()
-  command = command === 'node' ? command : path.resolve(cwd, 'node_modules', '.bin', command)
+  let args = options.shell
+    ? [command]
+    : (() => {
+        let args = command.split(' ')
+        command = args.shift()
+        command = command === 'node' ? command : path.resolve(cwd, 'node_modules', '.bin', command)
+        return [command, args]
+      })()
 
   let stdoutMessages = []
   let stderrMessages = []
@@ -55,7 +60,7 @@ module.exports = function $(command, options = {}) {
   }, 200)
 
   let runningProcess = new Promise((resolve, reject) => {
-    let child = spawn(command, args, {
+    let child = spawn(...args, {
       ...options,
       env: {
         ...process.env,

integrations/tailwindcss-cli/tests/integration.test.js

@@ -27,6 +27,23 @@ describe('static build', () => {
     )
   })
 
+  it('should be possible to pipe in data', async () => {
+    await writeInputFile('index.html', html`<div class="font-bold"></div>`)
+
+    await $('cat ./src/index.css | node ../../lib/cli.js -i - -o ./dist/main.css', {
+      shell: true,
+      env: { NODE_ENV: 'production' },
+    })
+
+    expect(await readOutputFile('main.css')).toIncludeCss(
+      css`
+        .font-bold {
+          font-weight: 700;
+        }
+      `
+    )
+  })
+
   it('should safelist a list of classes to always include', async () => {
     await writeInputFile('index.html', html`<div class="font-bold"></div>`)
     await writeInputFile(