use jest

.gitignore

@@ -1,3 +1,4 @@
 *.map
 /.vscode/*
-/tests/*.js
+/tests/*.js
+node_modules

jest.config.js

@@ -0,0 +1,9 @@
+  
+module.exports = {
+    transform: {
+      '^.+\\.ts?$': 'ts-jest'
+    },
+    testEnvironment: 'node',
+    testRegex: '/tests/.*\\.(test|spec)?\\.(ts|tsx|js)$',
+    moduleFileExtensions: ['ts', 'tsx', 'js', 'jsx', 'json', 'node']
+  };

package.json

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+{
+    "scripts": {
+        "test": "jest"
+    },
+    "devDependencies": {
+        "@types/jest": "^25.1.3",
+        "jest": "^25.1.0",
+        "ts-jest": "^25.2.1",
+        "typescript": "^3.8.2"
+    }
+}

tests/descriptiveCounter.test.ts

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+import { descriptiveCounter } from "../descriptiveCounter";
+
+describe('descriptiveCounter', function () {
+    it('one blankspace', function () {
+        let result = descriptiveCounter(" ");
+        expect(result).toBe("one blankspace");
+    });
+
+    it('mixed chars', function () {
+        let result = descriptiveCounter(" A ");
+        expect(result).toBe("one blankspace & one 'A' & one blankspace");
+    });
+
+    it('4 blankspaces', function () {
+        let result = descriptiveCounter("    ");
+        expect(result).toBe("four blankspaces");
+    });
+
+    it('9 blankspaces', function () {
+        let result = descriptiveCounter("         ");
+        expect(result).toBe("many blankspaces");
+    });
+
+    it('2 As', function () {
+        let result = descriptiveCounter("AA");
+        expect(result).toBe("two 'A's");
+    });
+});

tests/descriptiveCounterTests.ts

@@ -1,30 +0,0 @@
-import { descriptiveCounter } from "../descriptiveCounter";
-import { assert } from "./assert";
-
-let testCount: number = 0;
-
-type StringCallback = (text: string) => string;
-
-var showUnitTests = true;//window.location.href.indexOf("http") < 0;
-export function testDescriptiveCounter() {
-    if (showUnitTests) {
-        testCount = 0;
-        start();
-        console.log("total tests: " + testCount);
-    }
-}
-
-function start() {
-    console.log("=== descriptiveCounter ===");
-    test(descriptiveCounter, "one blankspace", " ", "one blankspace");
-    test(descriptiveCounter, "mixed chars", " A ", "one blankspace & one 'A' & one blankspace");
-    test(descriptiveCounter, "4 blankspaces", "    ", "four blankspaces");
-    test(descriptiveCounter, "9 blankspaces", "         ", "many blankspaces");
-    test(descriptiveCounter, "2 As", "AA", "two 'A's");
-}
-
-function test(func: StringCallback, testName: string, inputs, expected: string) {
-    let actual: string = func(inputs);
-    assert(testName, expected, actual);
-    testCount++;
-}