1 files changed, 27 insertions, 9 deletions
diff --git a/spec/ruby/core/gc/stat_spec.rb b/spec/ruby/core/gc/stat_spec.rb
index eb71fd9691..6e4800b3e3 100644
--- a/spec/ruby/core/gc/stat_spec.rb
+++ b/spec/ruby/core/gc/stat_spec.rb
@@ -3,16 +3,26 @@ require_relative '../../spec_helper'
 describe "GC.stat" do
   it "returns hash of values" do
     stat = GC.stat
-    stat.should be_kind_of(Hash)
+    stat.should.is_a?(Hash)
     stat.keys.should.include?(:count)
   end
 
+  it "updates the given hash values" do
+    hash = { count: "hello", __other__: "world" }
+    stat = GC.stat(hash)
+
+    stat.should.is_a?(Hash)
+    stat.should.equal? hash
+    stat[:count].should.is_a?(Integer)
+    stat[:__other__].should == "world"
+  end
+
   it "the values are all Integer since rb_gc_stat() returns size_t" do
-    GC.stat.values.each { |value| value.should be_kind_of(Integer) }
+    GC.stat.values.each { |value| value.should.is_a?(Integer) }
   end
 
   it "can return a single value" do
-    GC.stat(:count).should be_kind_of(Integer)
+    GC.stat(:count).should.is_a?(Integer)
   end
 
   it "increases count after GC is run" do
@@ -28,17 +38,25 @@ describe "GC.stat" do
   end
 
   it "provides some number for count" do
-    GC.stat(:count).should be_kind_of(Integer)
-    GC.stat[:count].should be_kind_of(Integer)
+    GC.stat(:count).should.is_a?(Integer)
+    GC.stat[:count].should.is_a?(Integer)
   end
 
   it "provides some number for heap_free_slots" do
-    GC.stat(:heap_free_slots).should be_kind_of(Integer)
-    GC.stat[:heap_free_slots].should be_kind_of(Integer)
+    GC.stat(:heap_free_slots).should.is_a?(Integer)
+    GC.stat[:heap_free_slots].should.is_a?(Integer)
   end
 
   it "provides some number for total_allocated_objects" do
-    GC.stat(:total_allocated_objects).should be_kind_of(Integer)
-    GC.stat[:total_allocated_objects].should be_kind_of(Integer)
+    GC.stat(:total_allocated_objects).should.is_a?(Integer)
+    GC.stat[:total_allocated_objects].should.is_a?(Integer)
+  end
+
+  it "raises an error if argument is not nil, a symbol, or a hash" do
+    -> { GC.stat(7) }.should.raise(TypeError, "non-hash or symbol given")
+  end
+
+  it "raises an error if an unknown key is given" do
+    -> { GC.stat(:foo) }.should.raise(ArgumentError, "unknown key: foo")
   end
 end