1 files changed, 62 insertions, 0 deletions
diff --git a/spec/ruby/library/stringio/truncate_spec.rb b/spec/ruby/library/stringio/truncate_spec.rb
new file mode 100644
index 0000000000..7205261141
--- /dev/null
+++ b/spec/ruby/library/stringio/truncate_spec.rb
@@ -0,0 +1,62 @@
+require_relative '../../spec_helper'
+require "stringio"
+
+describe "StringIO#truncate when passed [length]" do
+  before :each do
+    @io = StringIO.new(+'123456789')
+  end
+
+  it "returns an Integer" do
+    @io.truncate(4).should.is_a?(Integer)
+  end
+
+  it "truncated the underlying string down to the passed length" do
+    @io.truncate(4)
+    @io.string.should == "1234"
+  end
+
+  it "does not create a copy of the underlying string" do
+    io = StringIO.new(str = +"123456789")
+    io.truncate(4)
+    io.string.should.equal?(str)
+  end
+
+  it "does not change the position" do
+    @io.pos = 7
+    @io.truncate(4)
+    @io.pos.should.eql?(7)
+  end
+
+  it "can grow a string to a larger size, padding it with \\000" do
+    @io.truncate(12)
+    @io.string.should == "123456789\000\000\000"
+  end
+
+  it "raises an Errno::EINVAL when the passed length is negative" do
+    -> { @io.truncate(-1) }.should.raise(Errno::EINVAL)
+    -> { @io.truncate(-10) }.should.raise(Errno::EINVAL)
+  end
+
+  it "tries to convert the passed length to an Integer using #to_int" do
+    obj = mock("to_int")
+    obj.should_receive(:to_int).and_return(4)
+
+    @io.truncate(obj)
+    @io.string.should == "1234"
+  end
+
+  it "raises a TypeError when the passed length can't be converted to an Integer" do
+    -> { @io.truncate(Object.new) }.should.raise(TypeError)
+  end
+end
+
+describe "StringIO#truncate when self is not writable" do
+  it "raises an IOError" do
+    io = StringIO.new(+"test", "r")
+    -> { io.truncate(2) }.should.raise(IOError)
+
+    io = StringIO.new(+"test")
+    io.close_write
+    -> { io.truncate(2) }.should.raise(IOError)
+  end
+end