1 files changed, 85 insertions, 0 deletions
diff --git a/spec/ruby/core/kernel/singleton_method_spec.rb b/spec/ruby/core/kernel/singleton_method_spec.rb
new file mode 100644
index 0000000000..7d63fa7cc6
--- /dev/null
+++ b/spec/ruby/core/kernel/singleton_method_spec.rb
@@ -0,0 +1,85 @@
+require_relative '../../spec_helper'
+
+describe "Kernel#singleton_method" do
+  it "finds a method defined on the singleton class" do
+    obj = Object.new
+    def obj.foo; end
+    obj.singleton_method(:foo).should be_an_instance_of(Method)
+  end
+
+  it "returns a Method which can be called" do
+    obj = Object.new
+    def obj.foo; 42; end
+    obj.singleton_method(:foo).call.should == 42
+  end
+
+  it "only looks at singleton methods and not at methods in the class" do
+    klass = Class.new do
+      def foo
+        42
+      end
+    end
+    obj = klass.new
+    obj.foo.should == 42
+    -> {
+      obj.singleton_method(:foo)
+    }.should raise_error(NameError) { |e|
+      # a NameError and not a NoMethodError
+      e.class.should == NameError
+    }
+  end
+
+  it "raises a NameError if there is no such method" do
+    obj = Object.new
+    -> {
+      obj.singleton_method(:not_existing)
+    }.should raise_error(NameError) { |e|
+      # a NameError and not a NoMethodError
+      e.class.should == NameError
+    }
+  end
+
+  ruby_bug "#20620", ""..."3.4" do
+    it "finds a method defined in a module included in the singleton class" do
+      m = Module.new do
+        def foo
+          :foo
+        end
+      end
+
+      obj = Object.new
+      obj.singleton_class.include(m)
+
+      obj.singleton_method(:foo).should be_an_instance_of(Method)
+      obj.singleton_method(:foo).call.should == :foo
+    end
+
+    it "finds a method defined in a module prepended in the singleton class" do
+      m = Module.new do
+        def foo
+          :foo
+        end
+      end
+
+      obj = Object.new
+      obj.singleton_class.prepend(m)
+
+      obj.singleton_method(:foo).should be_an_instance_of(Method)
+      obj.singleton_method(:foo).call.should == :foo
+    end
+
+    it "finds a method defined in a module that an object is extended with" do
+      m = Module.new do
+        def foo
+          :foo
+        end
+      end
+
+      obj = Object.new
+      obj.extend(m)
+
+      obj.singleton_method(:foo).should be_an_instance_of(Method)
+      obj.singleton_method(:foo).call.should == :foo
+    end
+  end
+end