Added L0 tests and fixed some minor issues. (#20)

jest.config.js

@@ -0,0 +1,18 @@
+module.exports = {
+  clearMocks: true,
+  moduleFileExtensions: ['js', 'ts'],
+  testEnvironment: 'node',
+  testMatch: ['**/*.test.ts'],
+  transform: {
+    '^.+\\.ts$': 'ts-jest'
+  },
+  verbose: true,
+  coverageThreshold: {
+    "global": {
+      "branches": 0,
+      "functions": 14,
+      "lines": 27,
+      "statements": 27
+    }
+  }
+}