Implement Optional (sort of)

1 files changed, 21 insertions, 2 deletions

diff --git a/spec/parcom_spec.cr b/spec/parcom_spec.cr
index d9af3b9..2f3f6ba 100644
--- a/spec/parcom_spec.cr
+++ b/spec/parcom_spec.cr
@@ -348,7 +348,7 @@ describe Recover do
       result.value.should eq('t')
     end
 
-    it "succeeds and returns the default value without modifying the input of the wrapped parser fails" do
+    it "succeeds and returns the default value without modifying the input if the wrapped parser fails" do
       tokens = TokenStream.from_string("_____")
       result = p.parse(tokens)
 
@@ -358,7 +358,26 @@ describe Recover do
   end
 end
 
-pending Optional do
+describe Optional do
+  p = Optional.new(Token.new('t'))
+
+  describe "#parse" do
+    it "succeeds and returns the wrapped parser's value if it succeeds" do
+      tokens = TokenStream.from_string("testing")
+      result = p.parse(tokens)
+
+      result.tokens.should eq(tokens[1..])
+      result.value.should eq('t')
+    end
+
+    it "succeeds and returns a value of `nil` without modifying the input if the wrapped parser fails" do
+      tokens = TokenStream.from_string("_____")
+      result = p.parse(tokens)
+
+      result.tokens.should eq(tokens)
+      result.value.should be_nil
+    end
+  end
 end
 
 pending Tokens do