Add test case to check that lhs isn't undefined

src/test/scala/com/melvic/dry/tests/ParserSpec.scala

@@ -11,7 +11,7 @@ import org.scalatest.matchers.should
 import org.scalatestplus.scalacheck.ScalaCheckPropertyChecks
 
 /**
- * Houses the test cases for the parsing phase that are difficult to implement using Dry's tests (because the
+ * Houses the test cases for the parsing phase that are difficult to implement in Dry (because the
  * parser would fail in the first place).
  *
  * Note: many of the test cases here are based on the lox test suite:

tests/test_assignment.dry

@@ -13,11 +13,19 @@ def test_associativity() {
 def test_rhs() {
     let a = "before";
     let c = a = "after";
+
     assert_equal("a = 'after'", a, "after");
     assert_equal("c = 'after'", c, "after");
 }
 
+def test_lhs() {
+    assert_error("rhs should not be an undefined variable", Errors.UNDEFINED_VARIABLE,
+            lambda() { unknown = "what"; });
+}
+
 test_associativity();
+test_rhs();
+test_lhs();
 
 // global
 let a = "before";