1 files changed, 46 insertions, 0 deletions
diff --git a/spec/ruby/core/string/unpack_spec.rb b/spec/ruby/core/string/unpack_spec.rb
new file mode 100644
index 0000000000..eb4710ce14
--- /dev/null
+++ b/spec/ruby/core/string/unpack_spec.rb
@@ -0,0 +1,46 @@
+require_relative '../../spec_helper'
+
+describe "String#unpack" do
+  it "raises a TypeError when passed nil" do
+    -> { "abc".unpack(nil) }.should.raise(TypeError)
+  end
+
+  it "raises a TypeError when passed an Integer" do
+    -> { "abc".unpack(1) }.should.raise(TypeError)
+  end
+
+  it "starts unpacking from the given offset" do
+    "abc".unpack("CC", offset: 1).should == [98, 99]
+  end
+
+  it "traits offset as a bytes offset" do
+    "؈".unpack("CC").should == [216, 136]
+    "؈".unpack("CC", offset: 1).should == [136, nil]
+  end
+
+  describe "when the offset is negative" do
+    ruby_version_is "4.1" do
+      it "starts unpacking from the end" do
+        "abc".unpack("CC", offset: -2).should == [98, 99]
+      end
+
+      it "raises an ArgumentError if it is less than -length" do
+        -> { "a".unpack("C", offset: -2) }.should.raise(ArgumentError, "offset outside of string")
+      end
+    end
+
+    ruby_version_is ""..."4.1" do
+      it "raises an ArgumentError" do
+        -> { "a".unpack("C", offset: -1) }.should.raise(ArgumentError, "offset can't be negative")
+      end
+    end
+  end
+
+  it "returns nil if the offset is at the end of the string" do
+    "a".unpack("C", offset: 1).should == [nil]
+  end
+
+  it "raises an ArgumentError when the offset is larger than the string" do
+    -> { "a".unpack("C", offset: 2) }.should.raise(ArgumentError, "offset outside of string")
+  end
+end