Add Lint/Formatting rule

spec/ameba/rule/lint/formatting_spec.cr

@@ -0,0 +1,48 @@
+require "../../../spec_helper"
+
+module Ameba::Rule::Lint
+  describe Formatting do
+    subject = Formatting.new
+
+    it "passes if source is formatted" do
+      expect_no_issues subject, <<-CRYSTAL
+        def method(a, b)
+          a + b
+        end
+
+        CRYSTAL
+    end
+
+    it "reports if source is not formatted" do
+      expect_issue subject, <<-CRYSTAL
+        def method(a,b)
+        # ^{} error: Use built-in formatter to format this source
+        end
+        CRYSTAL
+    end
+
+    context "properties" do
+      context "#fail_on_error" do
+        it "passes on formatter errors by default" do
+          rule = Formatting.new
+
+          expect_no_issues rule, <<-CRYSTAL
+            def method(a, b)
+              a + b
+            CRYSTAL
+        end
+
+        it "reports on formatter errors when enabled" do
+          rule = Formatting.new
+          rule.fail_on_error = true
+
+          expect_issue rule, <<-CRYSTAL
+            def method(a, b)
+              a + b
+                 # ^ error: Error while formatting: expecting identifier 'end', not 'EOF'
+            CRYSTAL
+        end
+      end
+    end
+  end
+end