Add proper tests, exception handling, implement getAbstractName

src/runtime/javascript/tests/basic.test.ts

@@ -0,0 +1,16 @@
+import PGF from '../index'
+
+test('readPGF successful', () => {
+  let gr = PGF.readPGF('../haskell/tests/basic.pgf')
+})
+
+test('readPGF missing file', () => {
+  expect(() => {
+    PGF.readPGF('abc.pgf')
+  }).toThrow()
+})
+
+test('abstract name', () => {
+  let gr = PGF.readPGF('../haskell/tests/basic.pgf')
+  expect(gr.getAbstractName()).toBe('basic')
+})