New rule: trailing blank lines

spec/ameba/rules/trailing_blank_lines_spec.cr

@@ -0,0 +1,37 @@
+require "../../spec_helper"
+
+module Ameba::Rules
+  subject = TrailingBlankLines.new
+
+  describe TrailingBlankLines do
+    it "passes if there is no blank lines at the end" do
+      source = Source.new "", "no-blankline"
+      subject.catch(source).valid?.should be_true
+    end
+
+    it "fails if there is a blank line at the end of a source" do
+      source = Source.new "", "a = 1\n \n "
+      subject.catch(source).valid?.should be_false
+    end
+
+    it "passes if source is empty" do
+      source = Source.new "", ""
+      subject.catch(source).valid?.should be_true
+    end
+
+    it "passes if last line is not blank" do
+      source = Source.new "", "\n\n\n puts 22"
+      subject.catch(source).valid?.should be_true
+    end
+
+    it "reports rule, pos and message" do
+      source = Source.new "", "a = 1\n\n "
+      subject.catch(source)
+
+      error = source.errors.first
+      error.rule.should_not be_nil
+      error.pos.should eq 3
+      error.message.should eq "Blank lines detected at the end of the file"
+    end
+  end
+end