1 files changed, 54 insertions, 0 deletions
diff --git a/spec/ruby/core/kernel/trace_var_spec.rb b/spec/ruby/core/kernel/trace_var_spec.rb
new file mode 100644
index 0000000000..150c3da266
--- /dev/null
+++ b/spec/ruby/core/kernel/trace_var_spec.rb
@@ -0,0 +1,54 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Kernel#trace_var" do
+  before :each do
+    $Kernel_trace_var_global = nil
+  end
+
+  after :each do
+    untrace_var :$Kernel_trace_var_global
+
+    $Kernel_trace_var_global = nil
+    $Kernel_trace_var_extra  = nil
+  end
+
+  it "is a private method" do
+    Kernel.private_instance_methods(false).should.include?(:trace_var)
+  end
+
+  it "hooks assignments to a global variable" do
+    captured = nil
+
+    trace_var :$Kernel_trace_var_global do |value|
+      captured = value
+    end
+
+    $Kernel_trace_var_global = 'foo'
+    captured.should == 'foo'
+  end
+
+  it "accepts a proc argument instead of a block" do
+    captured = nil
+
+    trace_var :$Kernel_trace_var_global, proc {|value| captured = value}
+
+    $Kernel_trace_var_global = 'foo'
+    captured.should == 'foo'
+  end
+
+  # String arguments should be evaluated in the context of the caller.
+  it "accepts a String argument instead of a Proc or block" do
+    trace_var :$Kernel_trace_var_global, '$Kernel_trace_var_extra = true'
+
+    $Kernel_trace_var_global = 'foo'
+
+    $Kernel_trace_var_extra.should == true
+  end
+
+  it "raises ArgumentError if no block or proc is provided" do
+    -> do
+      trace_var :$Kernel_trace_var_global
+    end.should.raise(ArgumentError)
+  end
+end