New rule: rand zero

spec/ameba/rule/rand_zero_spec.cr

@@ -0,0 +1,36 @@
+require "../../spec_helper"
+
+module Ameba::Rule
+  describe RandZero do
+    subject = RandZero.new
+
+    it "passes if it is not rand(1) or rand(0)" do
+      s = Source.new %(
+        rand(1.0)
+        rand(0.11)
+        rand(2)
+      )
+      subject.catch(s).should be_valid
+    end
+
+    it "fails if it is rand(0)" do
+      s = Source.new "rand(0)"
+      subject.catch(s).should_not be_valid
+    end
+
+    it "fails if it is rand(1)" do
+      s = Source.new "rand(1)"
+      subject.catch(s).should_not be_valid
+    end
+
+    it "reports rule, location and a message" do
+      s = Source.new "rand(1)", "source.cr"
+      subject.catch(s).should_not be_valid
+      error = s.errors.first
+
+      error.rule.should_not be_nil
+      error.location.to_s.should eq "source.cr:1:1"
+      error.message.should eq "rand(1) always returns 0"
+    end
+  end
+end