1 files changed, 113 insertions, 0 deletions

diff --git a/spec/ruby/core/basicobject/instance_exec_spec.rb b/spec/ruby/core/basicobject/instance_exec_spec.rb
new file mode 100644
index 0000000000..cfce9a65ad
--- /dev/null
+++ b/spec/ruby/core/basicobject/instance_exec_spec.rb
@@ -0,0 +1,113 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "BasicObject#instance_exec" do
+  it "is a public instance method" do
+    BasicObject.public_instance_methods(false).should.include?(:instance_exec)
+  end
+
+  it "sets self to the receiver in the context of the passed block" do
+    a = BasicObject.new
+    a.instance_exec { self }.equal?(a).should == true
+  end
+
+  it "passes arguments to the block" do
+    a = BasicObject.new
+    a.instance_exec(1) { |b| b }.should.equal?(1)
+  end
+
+  it "raises a LocalJumpError unless given a block" do
+    -> { "hola".instance_exec }.should.raise(LocalJumpError)
+  end
+
+  it "has an arity of -1" do
+    Object.new.method(:instance_exec).arity.should == -1
+  end
+
+  it "accepts arguments with a block" do
+    -> { "hola".instance_exec(4, 5) { |a,b| a + b } }.should_not.raise
+  end
+
+  it "doesn't pass self to the block as an argument" do
+    "hola".instance_exec { |o| o }.should == nil
+  end
+
+  it "passes any arguments to the block" do
+    Object.new.instance_exec(1,2) {|one, two| one + two}.should == 3
+  end
+
+  describe "with optional argument" do
+    it "does not destructure a single array argument" do
+      Object.new.instance_exec([1, 2, 3]) { |a = 99| a }.should == [1, 2, 3]
+    end
+  end
+
+  it "only binds the exec to the receiver" do
+    f = Object.new
+    f.instance_exec do
+      def foo
+        1
+      end
+    end
+    f.foo.should == 1
+    -> { Object.new.foo }.should.raise(NoMethodError)
+  end
+
+  # TODO: This should probably be replaced with a "should behave like" that uses
+  # the many scoping/binding specs from kernel/eval_spec, since most of those
+  # behaviors are the same for instance_exec. See also module_eval/class_eval.
+
+  it "binds self to the receiver" do
+    s = "hola"
+    (s == s.instance_exec { self }).should == true
+  end
+
+  it "binds the block's binding self to the receiver" do
+    s = "hola"
+    (s == s.instance_exec { eval "self", binding }).should == true
+  end
+
+  it "executes in the context of the receiver" do
+    "Ruby-fu".instance_exec { size }.should == 7
+    Object.class_eval { "Ruby-fu".instance_exec{ to_s } }.should == "Ruby-fu"
+  end
+
+  it "has access to receiver's instance variables" do
+    BasicObjectSpecs::IVars.new.instance_exec { @secret }.should == 99
+  end
+
+  it "sets class variables in the receiver" do
+    BasicObjectSpecs::InstExec.class_variables.should.include?(:@@count)
+    BasicObjectSpecs::InstExec.send(:class_variable_get, :@@count).should == 2
+  end
+
+  it "raises a TypeError when defining methods on an immediate" do
+    -> do
+      1.instance_exec { def foo; end }
+    end.should.raise(TypeError)
+    -> do
+      :foo.instance_exec { def foo; end }
+    end.should.raise(TypeError)
+  end
+
+  quarantine! do # Not clean, leaves cvars lying around to break other specs
+    it "scopes class var accesses in the caller when called on an Integer" do
+      # Integer can take instance vars
+      Integer.class_eval "@@__tmp_instance_exec_spec = 1"
+      (defined? @@__tmp_instance_exec_spec).should == nil
+
+      @@__tmp_instance_exec_spec = 2
+      1.instance_exec { @@__tmp_instance_exec_spec }.should == 2
+      Integer.__send__(:remove_class_variable, :@@__tmp_instance_exec_spec)
+    end
+  end
+
+  it "raises a TypeError when defining methods on numerics" do
+    -> do
+      (1.0).instance_exec { def foo; end }
+    end.should.raise(TypeError)
+    -> do
+      (1 << 64).instance_exec { def foo; end }
+    end.should.raise(TypeError)
+  end
+end