New rule: comparison to boolean

spec/ameba/rules/comparison_to_boolean_spec.cr

@@ -0,0 +1,113 @@
+require "../../spec_helper"
+
+module Ameba::Rules
+  subject = ComparisonToBoolean.new
+
+  describe ComparisonToBoolean do
+    it "passes if there is no comparison to boolean" do
+      source = Source.new %(
+        a = true
+
+        if a
+          :ok
+        end
+
+        if true
+          :ok
+        end
+
+        unless s.empty?
+          :ok
+        end
+
+        :ok if a
+
+        :ok if a != 1
+
+        :ok if a == "true"
+
+        case a
+        when true
+          :ok
+        when false
+          :not_ok
+        end
+      )
+      subject.catch(source).valid?.should be_true
+    end
+
+    context "boolean on the right" do
+      it "fails if there is == comparison to boolean" do
+        source = Source.new %(
+          if s.empty? == true
+            :ok
+          end
+        )
+        subject.catch(source).valid?.should be_false
+      end
+
+      it "fails if there is != comparison to boolean" do
+        source = Source.new %(
+          if a != false
+            :ok
+          end
+        )
+        subject.catch(source).valid?.should be_false
+      end
+
+      it "fails if there is case comparison to boolean" do
+        source = Source.new %(
+          a === true
+        )
+        subject.catch(source).valid?.should be_false
+      end
+
+      it "reports rule, pos and message" do
+        source = Source.new "a != true"
+        subject.catch(source)
+
+        error = source.errors.first
+        error.rule.should_not be_nil
+        error.pos.should eq 1
+        error.message.should eq "Comparison to a boolean is pointless"
+      end
+    end
+
+    context "boolean on the left" do
+      it "fails if there is == comparison to boolean" do
+        source = Source.new %(
+          if true == s.empty?
+            :ok
+          end
+        )
+        subject.catch(source).valid?.should be_false
+      end
+
+      it "fails if there is != comparison to boolean" do
+        source = Source.new %(
+          if false != a
+            :ok
+          end
+        )
+        subject.catch(source).valid?.should be_false
+      end
+
+      it "fails if there is case comparison to boolean" do
+        source = Source.new %(
+          true === a
+        )
+        subject.catch(source).valid?.should be_false
+      end
+
+      it "reports rule, pos and message" do
+        source = Source.new "true != a"
+        subject.catch(source)
+
+        error = source.errors.first
+        error.rule.should_not be_nil
+        error.pos.should eq 1
+        error.message.should eq "Comparison to a boolean is pointless"
+      end
+    end
+  end
+end