improve test coverage of error handling

Author: mikesamuel

test/unit/es6/Lexer.js

@@ -58,5 +58,22 @@ test('template lexer', {
     assert.equal(tokens('SELECT `"', '`'), '`,_');
     assert.equal(tokens('SELECT ```', '`'), '`,_');
     assert.equal(tokens('SELECT `\\`', '`'), '`,_');
+  },
+  'replay error': function () {
+    const lexer = Lexer.makeLexer();
+    assert.equal(lexer('SELECT '), null);
+    assert.throws(
+      () => lexer(' # '),
+      /^Error: Expected delimiter at " # "$/);
+    // Providing more input throws the same error.
+    assert.throws(
+      () => lexer(' '),
+      /^Error: Expected delimiter at " # "$/);
+  },
+  'unfinished escape squence': function () {
+    const lexer = Lexer.makeLexer();
+    assert.throws(
+      () => lexer('SELECT "\\'),
+      /^Error: Expected "\\\\" at "\\\\"$/);
   }
 });