From 8835f1de0dbc6a059a42fad78d4acbb0984b94e2 Mon Sep 17 00:00:00 2001
From: Matthew Hall <hallmatthew314@gmail.com>
Date: Wed, 8 Mar 2023 20:03:26 +1300
Subject: Implement Plus

---
 spec/parcom_spec.cr | 50 ++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 48 insertions(+), 2 deletions(-)

(limited to 'spec/parcom_spec.cr')

diff --git a/spec/parcom_spec.cr b/spec/parcom_spec.cr
index b2a3a80..f35465c 100644
--- a/spec/parcom_spec.cr
+++ b/spec/parcom_spec.cr
@@ -261,10 +261,56 @@ describe Map do
   end
 end
 
-pending Phrase do
+describe Plus do
+  describe "#parse" do
+    tokens = TokenStream.from_string("testing")
+    p_t = Token(Char).new('t')
+    p_e = Token(Char).new('e')
+    p_at = Token(Char).new('@')
+
+    it "fails if the first parser fails" do
+      p = p_at + p_e
+      expect_raises(ParserException) { p.parse(tokens) }
+    end
+
+    it "fails if the second parser fails" do
+      p = p_t + p_at
+      expect_raises(ParserException) { p.parse(tokens) }
+    end
+
+    it "fails if both parsers fail" do
+      p = p_at + p_at
+      expect_raises(ParserException) { p.parse(tokens) }
+    end
+
+    it "succeeds if both parsers succeed" do
+      p = p_t + p_e
+      result = p.parse(tokens)
+
+      result.tokens.should eq(tokens[2..])
+      result.value[0].should eq('t')
+      result.value[1].should eq('e')
+    end
+
+    it "evaluates parsers from left to right (left associative)" do
+      p_succeeds = p_t + p_e
+      p_fails = p_e + p_t
+
+      p_succeeds.parse(tokens) # should not raise an exception
+      expect_raises(ParserException) { p_fails.parse(tokens) }
+
+      p_s = Token(Char).new('s')
+
+      r = (p_t + p_e + p_s).parse(tokens) # should not raise an exception
+      r.value.should be_a({ {Char, Char}, Char})
+
+      r = (p_t + (p_e + p_s)).parse(tokens) # should not raise an exception
+      r.value.should be_a({Char, {Char, Char} })
+    end
+  end
 end
 
-pending Plus do
+pending Phrase do
 end
 
 pending Recover do
-- 
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