add: unit and integration testing

app/node_modules/istanbul-lib-instrument/src/index.js

@@ -0,0 +1,21 @@
+const { defaults } = require('@istanbuljs/schema');
+const Instrumenter = require('./instrumenter');
+const programVisitor = require('./visitor');
+const readInitialCoverage = require('./read-coverage');
+
+/**
+ * createInstrumenter creates a new instrumenter with the
+ * supplied options.
+ * @param {Object} opts - instrumenter options. See the documentation
+ * for the Instrumenter class.
+ */
+function createInstrumenter(opts) {
+    return new Instrumenter(opts);
+}
+
+module.exports = {
+    createInstrumenter,
+    programVisitor,
+    readInitialCoverage,
+    defaultOpts: defaults.instrumenter
+};