1 files changed, 222 insertions, 0 deletions
diff --git a/spec/ruby/core/method/arity_spec.rb b/spec/ruby/core/method/arity_spec.rb
new file mode 100644
index 0000000000..32a50a0999
--- /dev/null
+++ b/spec/ruby/core/method/arity_spec.rb
@@ -0,0 +1,222 @@
+require File.expand_path('../../../spec_helper', __FILE__)
+require File.expand_path('../fixtures/classes', __FILE__)
+
+describe "Method#arity" do
+  SpecEvaluate.desc = "for method definition"
+
+  context "returns zero" do
+    evaluate <<-ruby do
+        def m() end
+      ruby
+
+      method(:m).arity.should == 0
+    end
+
+    evaluate <<-ruby do
+        def n(&b) end
+      ruby
+
+      method(:n).arity.should == 0
+    end
+  end
+
+  context "returns positive values" do
+    evaluate <<-ruby do
+        def m(a) end
+        def n(a, b) end
+        def o(a, b, c) end
+        def p(a, b, c, d) end
+      ruby
+
+      method(:m).arity.should == 1
+      method(:n).arity.should == 2
+      method(:o).arity.should == 3
+      method(:p).arity.should == 4
+    end
+
+    evaluate <<-ruby do
+        def m(a:) end
+        def n(a:, b:) end
+        def o(a: 1, b:, c:, d: 2) end
+      ruby
+
+      method(:m).arity.should == 1
+      method(:n).arity.should == 1
+      method(:o).arity.should == 1
+    end
+
+    evaluate <<-ruby do
+        def m(a, b:) end
+        def n(a, b:, &l) end
+      ruby
+
+      method(:m).arity.should == 2
+      method(:n).arity.should == 2
+    end
+
+    evaluate <<-ruby do
+        def m(a, b, c:, d: 1) end
+        def n(a, b, c:, d: 1, **k, &l) end
+      ruby
+
+      method(:m).arity.should == 3
+      method(:n).arity.should == 3
+    end
+  end
+
+  context "returns negative values" do
+    evaluate <<-ruby do
+        def m(a=1) end
+        def n(a=1, b=2) end
+      ruby
+
+      method(:m).arity.should == -1
+      method(:n).arity.should == -1
+    end
+
+    evaluate <<-ruby do
+        def m(a, b=1) end
+        def n(a, b, c=1, d=2) end
+      ruby
+
+      method(:m).arity.should == -2
+      method(:n).arity.should == -3
+    end
+
+    evaluate <<-ruby do
+        def m(a=1, *b) end
+        def n(a=1, b=2, *c) end
+      ruby
+
+      method(:m).arity.should == -1
+      method(:n).arity.should == -1
+    end
+
+    evaluate <<-ruby do
+        def m(*) end
+        def n(*a) end
+      ruby
+
+      method(:m).arity.should == -1
+      method(:n).arity.should == -1
+    end
+
+    evaluate <<-ruby do
+        def m(a, *) end
+        def n(a, *b) end
+        def o(a, b, *c) end
+        def p(a, b, c, *d) end
+      ruby
+
+      method(:m).arity.should == -2
+      method(:n).arity.should == -2
+      method(:o).arity.should == -3
+      method(:p).arity.should == -4
+    end
+
+    evaluate <<-ruby do
+        def m(*a, b) end
+        def n(*a, b, c) end
+        def o(*a, b, c, d) end
+      ruby
+
+      method(:m).arity.should == -2
+      method(:n).arity.should == -3
+      method(:o).arity.should == -4
+    end
+
+    evaluate <<-ruby do
+        def m(a, *b, c) end
+        def n(a, b, *c, d, e) end
+      ruby
+
+      method(:m).arity.should == -3
+      method(:n).arity.should == -5
+    end
+
+    evaluate <<-ruby do
+        def m(a, b=1, c=2, *d, e, f) end
+        def n(a, b, c=1, *d, e, f, g) end
+      ruby
+
+      method(:m).arity.should == -4
+      method(:n).arity.should == -6
+    end
+
+    evaluate <<-ruby do
+        def m(a: 1) end
+        def n(a: 1, b: 2) end
+      ruby
+
+      method(:m).arity.should == -1
+      method(:n).arity.should == -1
+    end
+
+    evaluate <<-ruby do
+        def m(a=1, b: 2) end
+        def n(*a, b: 1) end
+        def o(a=1, b: 2) end
+        def p(a=1, *b, c: 2, &l) end
+      ruby
+
+      method(:m).arity.should == -1
+      method(:n).arity.should == -1
+      method(:o).arity.should == -1
+      method(:p).arity.should == -1
+    end
+
+    evaluate <<-ruby do
+        def m(**k, &l) end
+        def n(*a, **k) end
+        def o(a: 1, b: 2, **k) end
+      ruby
+
+      method(:m).arity.should == -1
+      method(:n).arity.should == -1
+      method(:o).arity.should == -1
+    end
+
+    evaluate <<-ruby do
+        def m(a=1, *b, c:, d: 2, **k, &l) end
+      ruby
+
+      method(:m).arity.should == -2
+    end
+
+    evaluate <<-ruby do
+        def m(a, b=1, *c, d, e:, f: 2, **k, &l) end
+        def n(a, b=1, *c, d:, e:, f: 2, **k, &l) end
+        def o(a=0, b=1, *c, d, e:, f: 2, **k, &l) end
+        def p(a=0, b=1, *c, d:, e:, f: 2, **k, &l) end
+      ruby
+
+      method(:m).arity.should == -4
+      method(:n).arity.should == -3
+      method(:o).arity.should == -3
+      method(:p).arity.should == -2
+    end
+  end
+
+  context "for a Method generated by respond_to_missing?" do
+    it "returns -1" do
+      obj = mock("method arity respond_to_missing")
+      obj.should_receive(:respond_to_missing?).and_return(true)
+
+      obj.method(:m).arity.should == -1
+    end
+  end
+
+  context "for a Method generated by attr_reader" do
+    it "return 0" do
+      obj = MethodSpecs::Methods.new
+      obj.method(:reader).arity.should == 0
+    end
+  end
+
+  context "for a Method generated by attr_writer" do
+    it "returns 1" do
+      obj = MethodSpecs::Methods.new
+      obj.method(:writer=).arity.should == 1
+    end
+  end
+end