Fix travis build & new rule: constant names (#14)

spec/ameba/rules/constant_names_spec.cr

@@ -0,0 +1,51 @@
+require "../../spec_helper"
+
+module Ameba
+  subject = Rules::ConstantNames.new
+
+  private def it_reports_constant(content, expected)
+    it "reports constant name #{expected}" do
+      s = Source.new content
+      Rules::ConstantNames.new.catch(s).should_not be_valid
+      s.errors.first.message.should contain expected
+    end
+  end
+
+  describe Rules::ConstantNames do
+    it "passes if type names are screaming-cased" do
+      s = Source.new %(
+        LUCKY_NUMBERS     = [3, 7, 11]
+        DOCUMENTATION_URL = "http://crystal-lang.org/docs"
+
+        Int32
+
+        s : String = "str"
+
+        def works(n : Int32)
+        end
+
+        a = 1
+        myVar = 2
+        m_var = 3
+      )
+      subject.catch(s).should be_valid
+    end
+
+    it_reports_constant "MyBadConstant=1", "MYBADCONSTANT"
+    it_reports_constant "Wrong_NAME=2", "WRONG_NAME"
+    it_reports_constant "Wrong_Name=3", "WRONG_NAME"
+
+    it "reports rule, pos and message" do
+      s = Source.new %(
+        Const = 1
+      )
+      subject.catch(s).should_not be_valid
+      error = s.errors.first
+      error.rule.should_not be_nil
+      error.pos.should eq 2
+      error.message.should eq(
+        "Constant name should be screaming-cased: CONST, not Const"
+      )
+    end
+  end
+end