1 files changed, 50 insertions, 0 deletions
diff --git a/spec/ruby/core/array/join_spec.rb b/spec/ruby/core/array/join_spec.rb
new file mode 100644
index 0000000000..e78ea6f9e1
--- /dev/null
+++ b/spec/ruby/core/array/join_spec.rb
@@ -0,0 +1,50 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+require_relative 'shared/join'
+
+describe "Array#join" do
+  it_behaves_like :array_join_with_string_separator,  :join
+  it_behaves_like :array_join_with_default_separator, :join
+
+  it "does not separate elements when the passed separator is nil" do
+    [1, 2, 3].join(nil).should == '123'
+  end
+
+  it "calls #to_str to convert the separator to a String" do
+    sep = mock("separator")
+    sep.should_receive(:to_str).and_return(", ")
+    [1, 2].join(sep).should == "1, 2"
+  end
+
+  it "does not call #to_str on the separator if the array is empty" do
+    sep = mock("separator")
+    sep.should_not_receive(:to_str)
+    [].join(sep).should == ""
+  end
+
+  it "raises a TypeError if the separator cannot be coerced to a String by calling #to_str" do
+    obj = mock("not a string")
+    -> { [1, 2].join(obj) }.should raise_error(TypeError)
+  end
+
+  it "raises a TypeError if passed false as the separator" do
+    -> { [1, 2].join(false) }.should raise_error(TypeError)
+  end
+end
+
+describe "Array#join with $," do
+  before :each do
+    @before_separator = $,
+  end
+
+  after :each do
+    suppress_warning {$, = @before_separator}
+  end
+
+  it "separates elements with default separator when the passed separator is nil" do
+    suppress_warning {
+      $, = "_"
+      [1, 2, 3].join(nil).should == '1_2_3'
+    }
+  end
+end