add spec for Interpreter#initialize

spec/crisp/interpreter_spec.cr

@@ -1,6 +1,28 @@
 require "../helper"
 
 describe "Crisp::Interpreter" do
+  describe "#initialize" do
+    it "takes arguments as string value" do
+      i = Crisp::Interpreter.new %w(foo bar baz)
+      result = i.eval_string("*ARGV*")
+      result.should be_a(Crisp::Type)
+      unwrapped = result.unwrap
+      unwrapped.should be_a(Crisp::List)
+      if unwrapped.is_a? Crisp::List
+        unwrapped.size.should eq(3)
+        a0 = unwrapped[0].unwrap
+        a1 = unwrapped[1].unwrap
+        a2 = unwrapped[2].unwrap
+        a0.should be_a(String)
+        a1.should be_a(String)
+        a2.should be_a(String)
+        a0.should eq("foo")
+        a1.should eq("bar")
+        a2.should eq("baz")
+      end
+    end
+  end
+
   describe "#eval_string" do
     it "evaluates string of Crisp expression" do
       i = Crisp::Interpreter.new
@@ -14,8 +36,9 @@ describe "Crisp::Interpreter" do
 
   describe "#run" do
     it "raises eval error with file which doesn't exist" do
+      i = Crisp::Interpreter.new
       expect_raises Crisp::EvalException do
-        Crisp::Interpreter.new "/non/existent/file"
+        i.run "/non/existent/file"
       end
     end
   end