From b61aba7186cb7c616d6c8f9a3b9e6442173cbbf6 Mon Sep 17 00:00:00 2001
From: Matthew Hall <hallmatthew314@gmail.com>
Date: Wed, 8 Mar 2023 20:53:17 +1300
Subject: Implement Optional (sort of)

---
 spec/parcom_spec.cr | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

(limited to 'spec')

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
-- 
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