1 files changed, 155 insertions, 0 deletions
diff --git a/spec/ruby/core/array/sample_spec.rb b/spec/ruby/core/array/sample_spec.rb
new file mode 100644
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+++ b/spec/ruby/core/array/sample_spec.rb
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+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Array#sample" do
+  it "samples evenly" do
+    ArraySpecs.measure_sample_fairness(4, 1, 400)
+    ArraySpecs.measure_sample_fairness(4, 2, 400)
+    ArraySpecs.measure_sample_fairness(4, 3, 400)
+    ArraySpecs.measure_sample_fairness(40, 3, 400)
+    ArraySpecs.measure_sample_fairness(40, 4, 400)
+    ArraySpecs.measure_sample_fairness(40, 8, 400)
+    ArraySpecs.measure_sample_fairness(40, 16, 400)
+    ArraySpecs.measure_sample_fairness_large_sample_size(100, 80, 4000)
+  end
+
+  it "returns nil for an empty Array" do
+    [].sample.should be_nil
+  end
+
+  it "returns nil for an empty array when called without n and a Random is given" do
+    [].sample(random: Random.new(42)).should be_nil
+  end
+
+  it "returns a single value when not passed a count" do
+    [4].sample.should equal(4)
+  end
+
+  it "returns a single value when not passed a count and a Random is given" do
+    [4].sample(random: Random.new(42)).should equal(4)
+  end
+
+  it "returns a single value when not passed a count and a Random class is given" do
+    [4].sample(random: Random).should equal(4)
+  end
+
+  it "returns an empty Array when passed zero" do
+    [4].sample(0).should == []
+  end
+
+  it "returns an Array of elements when passed a count" do
+    [1, 2, 3, 4].sample(3).should be_an_instance_of(Array)
+  end
+
+  it "returns elements from the Array" do
+    array = [1, 2, 3, 4]
+    array.sample(3).all? { |x| array.should include(x) }
+  end
+
+  it "returns at most the number of elements in the Array" do
+    array = [1, 2, 3, 4]
+    result = array.sample(20)
+    result.size.should == 4
+  end
+
+  it "does not return the same value if the Array has unique values" do
+    array = [1, 2, 3, 4]
+    result = array.sample(20)
+    result.sort.should == array
+  end
+
+  it "may return the same value if the array is not unique" do
+    [4, 4].sample(2).should == [4,4]
+  end
+
+  it "calls #to_int to convert the count when passed an Object" do
+    [1, 2, 3, 4].sample(mock_int(2)).size.should == 2
+  end
+
+  it "raises ArgumentError when passed a negative count" do
+    -> { [1, 2].sample(-1) }.should raise_error(ArgumentError)
+  end
+
+  it "does not return subclass instances with Array subclass" do
+    ArraySpecs::MyArray[1, 2, 3].sample(2).should be_an_instance_of(Array)
+  end
+
+  describe "with options" do
+    it "calls #rand on the Object passed by the :random key in the arguments Hash" do
+      obj = mock("array_sample_random")
+      obj.should_receive(:rand).and_return(0.5)
+
+      [1, 2].sample(random: obj).should be_an_instance_of(Integer)
+    end
+
+    it "raises a NoMethodError if an object passed for the RNG does not define #rand" do
+      obj = BasicObject.new
+
+      -> { [1, 2].sample(random: obj) }.should raise_error(NoMethodError)
+    end
+
+    describe "when the object returned by #rand is an Integer" do
+      it "uses the integer as index" do
+        random = mock("array_sample_random_ret")
+        random.should_receive(:rand).and_return(0)
+
+        [1, 2].sample(random: random).should == 1
+
+        random = mock("array_sample_random_ret")
+        random.should_receive(:rand).and_return(1)
+
+        [1, 2].sample(random: random).should == 2
+      end
+
+      it "raises a RangeError if the value is less than zero" do
+        random = mock("array_sample_random")
+        random.should_receive(:rand).and_return(-1)
+
+        -> { [1, 2].sample(random: random) }.should raise_error(RangeError)
+      end
+
+      it "raises a RangeError if the value is equal to the Array size" do
+        random = mock("array_sample_random")
+        random.should_receive(:rand).and_return(2)
+
+        -> { [1, 2].sample(random: random) }.should raise_error(RangeError)
+      end
+
+      it "raises a RangeError if the value is greater than the Array size" do
+        random = mock("array_sample_random")
+        random.should_receive(:rand).and_return(3)
+
+        -> { [1, 2].sample(random: random) }.should raise_error(RangeError)
+      end
+    end
+  end
+
+  describe "when the object returned by #rand is not an Integer but responds to #to_int" do
+    it "calls #to_int on the Object" do
+      value = mock("array_sample_random_value")
+      value.should_receive(:to_int).and_return(1)
+      random = mock("array_sample_random")
+      random.should_receive(:rand).and_return(value)
+
+      [1, 2].sample(random: random).should == 2
+    end
+
+    it "raises a RangeError if the value is less than zero" do
+      value = mock("array_sample_random_value")
+      value.should_receive(:to_int).and_return(-1)
+      random = mock("array_sample_random")
+      random.should_receive(:rand).and_return(value)
+
+      -> { [1, 2].sample(random: random) }.should raise_error(RangeError)
+    end
+
+    it "raises a RangeError if the value is equal to the Array size" do
+      value = mock("array_sample_random_value")
+      value.should_receive(:to_int).and_return(2)
+      random = mock("array_sample_random")
+      random.should_receive(:rand).and_return(value)
+
+      -> { [1, 2].sample(random: random) }.should raise_error(RangeError)
+    end
+  end
+end