Second attempt

lib/getThreads.js

@@ -9,26 +9,23 @@ const THREADS = CPUS > 2 ? CPUS - 1 : 1;
 function getThreads(config) {
   const { threads } = config;
 
-  const defaultCheck = threads === 'auto' ||
-    threads === -1 ||
-    threads === '' ||
-    threads === true ||
-    threads === null ||
-    typeof threads === 'undefined';
-
-  if (defaultCheck) {
-    return THREADS;
-  }
-
-  if (threads === 0 || threads === 1 || threads === false) {
-    return 1;
+  switch (threads) {
+    case 'auto':
+    case -1:
+    case '':
+    case true:
+    case null:
+    case undefined:
+      return THREADS;
+    case 0:
+    case 1:
+    case false:
+      return 1;
+    default:
+      if (threads > 1) {
+        return threads;
+      }
   }
-
-  if (threads > 1) {
-    return threads;
-  }
-
-  throw new Error(`Invalid threads option! (${threads})`);
 }
 
 module.exports = getThreads;

test/threads_test.js

@@ -12,7 +12,7 @@ describe('getThreads', () => {
   it('should use the number of available threads -1', done => {
     const config = {};
 
-    for (const option of ['auto', true, -1, '', null, undefined]) {
+    for (const option of ['auto', -1, '', true, null, undefined]) {
       config.threads = option;
       const expected = THREADS;
       const actual = getThreads(config);
@@ -23,14 +23,16 @@ describe('getThreads', () => {
     done();
   });
 
-  it('should return 1 with `threads: false`', done => {
-    const config = {
-      threads: false
-    };
-    const expected = 1;
-    const actual = getThreads(config);
+  it('should return 1 with false, 0, or 1', done => {
+    const config = {};
+
+    for (const option of [0, 1, false]) {
+      config.threads = option;
+      const expected = 1;
+      const actual = getThreads(config);
+      assert.equal(actual, expected);
+    }
 
-    assert.equal(actual, expected);
     done();
   });
 
@@ -44,16 +46,4 @@ describe('getThreads', () => {
     assert.equal(actual, expected);
     done();
   });
-
-  it('should throw an error with invalid threads option', done => {
-    const config = {};
-
-    for (const option of [-2, 'foo']) {
-      config.threads = option;
-      const expected = () => getThreads(config);
-      assert.throws(expected, /^Error: Invalid threads/, `"thread: ${option}" failed!`);
-    }
-
-    done();
-  });
 });