1 files changed, 72 insertions, 0 deletions
diff --git a/spec/ruby/library/stringio/ungetc_spec.rb b/spec/ruby/library/stringio/ungetc_spec.rb
new file mode 100644
index 0000000000..8753ac9666
--- /dev/null
+++ b/spec/ruby/library/stringio/ungetc_spec.rb
@@ -0,0 +1,72 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "StringIO#ungetc when passed [char]" do
+  before :each do
+    @io = StringIO.new(+'1234')
+  end
+
+  it "writes the passed char before the current position" do
+    @io.pos = 1
+    @io.ungetc(?A)
+    @io.string.should == 'A234'
+  end
+
+  it "returns nil" do
+    @io.pos = 1
+    @io.ungetc(?A).should == nil
+  end
+
+  it "decreases the current position by one" do
+    @io.pos = 2
+    @io.ungetc(?A)
+    @io.pos.should.eql?(1)
+  end
+
+  it "pads with \\000 when the current position is after the end" do
+    @io.pos = 15
+    @io.ungetc(?A)
+    @io.string.should == "1234\000\000\000\000\000\000\000\000\000\000A"
+  end
+
+  it "tries to convert the passed argument to an String using #to_str" do
+    obj = mock("to_str")
+    obj.should_receive(:to_str).and_return(?A)
+
+    @io.pos = 1
+    @io.ungetc(obj)
+    @io.string.should == "A234"
+  end
+
+  it "raises a TypeError when the passed length can't be converted to an Integer or String" do
+    -> { @io.ungetc(Object.new) }.should.raise(TypeError)
+  end
+end
+
+describe "StringIO#ungetc when self is not readable" do
+  it "raises an IOError" do
+    io = StringIO.new(+"test", "w")
+    io.pos = 1
+    -> { io.ungetc(?A) }.should.raise(IOError)
+
+    io = StringIO.new(+"test")
+    io.pos = 1
+    io.close_read
+    -> { io.ungetc(?A) }.should.raise(IOError)
+  end
+end
+
+# Note: This is incorrect.
+#
+# describe "StringIO#ungetc when self is not writable" do
+#   it "raises an IOError" do
+#     io = StringIO.new(+"test", "r")
+#     io.pos = 1
+#     lambda { io.ungetc(?A) }.should.raise(IOError)
+#
+#     io = StringIO.new(+"test")
+#     io.pos = 1
+#     io.close_write
+#     lambda { io.ungetc(?A) }.should.raise(IOError)
+#   end
+# end