(fix/test): wrap shell.grep bc it shouldn't always succeed

- regular grep will have an error code if it failed to match, but
  shell.grep doesn't, at least not when silent (maybe it shouldn't
  be silent? that might be too noisy)
  - so add a wrapper that checks that stdout also has the pattern that
    was being matched (grep outputs line:pattern for each match)

Co-Authored-By: Anton Gilgur <agilgur5@gmail.com>

test/integration/tsdx-build-withBabel.test.js

@@ -1,7 +1,7 @@
 const shell = require('shelljs');
 
 const util = require('../utils/fixture');
-const { execWithCache } = require('../utils/shell');
+const { execWithCache, grep } = require('../utils/shell');
 
 shell.config.silent = false;
 
@@ -16,32 +16,32 @@ describe('integration :: tsdx build :: .babelrc.js', () => {
   });
 
   it('should convert styled-components template tags', () => {
-    let output = execWithCache('node ../dist/index.js build');
+    const output = execWithCache('node ../dist/index.js build');
     expect(output.code).toBe(0);
 
     // from styled.h1` to styled.h1(
-    output = shell.grep(/styled.h1\(/, ['dist/build-withbabel.*.js']);
-    expect(output.code).toBe(0);
+    const matched = grep(/styled.h1\(/, ['dist/build-withbabel.*.js']);
+    expect(matched).toBeTruthy();
   });
 
   // TODO: make this test work by allowing customization of plugin order
   it.skip('should remove comments in the CSS', () => {
-    let output = execWithCache('node ../dist/index.js build');
+    const output = execWithCache('node ../dist/index.js build');
     expect(output.code).toBe(0);
 
     // the "should be removed" comment shouldn't be there (gets error code)
-    output = shell.grep(/should be removed/, ['dist/build-withbabel.*.js']);
-    expect(output.code).toBe(1);
+    const matched = grep(/should be removed/, ['dist/build-withbabel.*.js']);
+    expect(matched).toBeTruthy();
   });
 
   it('should add an import of regeneratorRuntime', () => {
-    let output = execWithCache('node ../dist/index.js build');
+    const output = execWithCache('node ../dist/index.js build');
     expect(output.code).toBe(0);
 
-    output = shell.grep(/@babel\/runtime\/regenerator/, [
+    const matched = grep(/@babel\/runtime\/regenerator/, [
       'dist/build-withbabel.*.js',
     ]);
-    expect(output.code).toBe(0);
+    expect(matched).toBeTruthy();
   });
 
   it('should compile files into a dist directory', () => {

test/utils/shell.js

@@ -24,6 +24,19 @@ function execWithCache(command, { noCache = false } = {}) {
   return output;
 }
 
+// shelljs.grep wrapper
+// @param {RegExp} pattern
+// @param {string} fileName
+// @returns {boolean} true if pattern has matches in file
+function grep(pattern, fileName) {
+  const output = shell.grep(pattern, fileName);
+  // output.code is always 0 regardless of matched/unmatched patterns
+  // so need to test output.stdout
+  // https://github.com/jaredpalmer/tsdx/pull/525#discussion_r395571779
+  return Boolean(output.stdout.match(pattern));
+}
+
 module.exports = {
   execWithCache,
+  grep,
 };