spec/dendroid/syntax/choice_spec.rb in dendroid-0.0.7 vs spec/dendroid/syntax/choice_spec.rb in dendroid-0.0.8

@@ -49,6 +49,20 @@
       my_alt2 = Dendroid::Syntax::SymbolSeq.new([foo_symb, minus_symb, expr_symb])
       instance = described_class.new(foo_symb, [my_alt1, my_alt2])
       expect(instance.nonterminals).to eq([expr_symb, foo_symb])
     end
   end # context
+
+  context 'Errors:' do
+    it 'fails when initialized with one alternative only' do
+      err = StandardError
+      err_msg = 'The choice for `expression` must have at least two alternatives.'
+      expect { described_class.new(expr_symb, [alt1]) }.to raise_error(err, err_msg)
+    end
+
+    it 'fails in presence of duplicate rhs' do
+      err = StandardError
+      err_msg = 'Duplicate alternatives: expression => NUMBER PLUS NUMBER'
+      expect { described_class.new(expr_symb, [alt1, alt2, alt1]) }.to raise_error(err, err_msg)
+    end
+  end # context
 end # describe