Run tests only when they are detected on the disk. Do not run tests when the test file pattern is invalid. Require to set KNAPSACK_PRO_TEST_FILE_PATTERN

package.json

@@ -51,7 +51,7 @@
     "knapsack-pro-jest": "lib/knapsack-pro-jest.js"
   },
   "dependencies": {
-    "@knapsack-pro/core": "^1.6.0",
+    "@knapsack-pro/core": "^1.6.1",
     "glob": "^7.1.3",
     "jest": "^24.8.0",
     "minimatch": "^3.0.4",

src/test-files-finder.ts

@@ -1,12 +1,12 @@
 import glob = require('glob');
 import minimatch = require('minimatch');
 
-import { TestFile } from '@knapsack-pro/core';
+import { KnapsackProLogger, TestFile } from '@knapsack-pro/core';
 import { EnvConfig } from './env-config';
 
 export class TestFilesFinder {
   public static allTestFiles(): TestFile[] {
-    return glob
+    const testFiles = glob
       .sync(EnvConfig.testFilePattern)
       .filter((testFilePath: string) => {
         if (EnvConfig.testFileExcludePattern) {
@@ -22,5 +22,18 @@ export class TestFilesFinder {
         return !testFilePath.match(/node_modules/);
       })
       .map((testFilePath: string) => ({ path: testFilePath }));
+
+    if (testFiles.length === 0) {
+      const knapsackProLogger = new KnapsackProLogger();
+
+      const errorMessage =
+        // tslint:disable-next-line: max-line-length
+        'Test files cannot be found.\nPlease set KNAPSACK_PRO_TEST_FILE_PATTERN matching your test directory structure.\nLearn more: https://github.com/KnapsackPro/knapsack-pro-jest#how-to-run-tests-only-from-specific-directory';
+
+      knapsackProLogger.error(errorMessage);
+      throw errorMessage;
+    }
+
+    return testFiles;
   }
 }