1 files changed, 71 insertions, 0 deletions
diff --git a/spec/ruby/core/rational/truncate_spec.rb b/spec/ruby/core/rational/truncate_spec.rb
new file mode 100644
index 0000000000..3614431a7f
--- /dev/null
+++ b/spec/ruby/core/rational/truncate_spec.rb
@@ -0,0 +1,71 @@
+require_relative "../../spec_helper"
+
+describe "Rational#truncate" do
+  before do
+    @rational = Rational(2200, 7)
+  end
+
+  describe "with no arguments (precision = 0)" do
+    it "returns an integer" do
+      @rational.truncate.should.is_a?(Integer)
+    end
+
+    it "returns the truncated value toward 0" do
+      @rational.truncate.should == 314
+      Rational(1, 2).truncate.should == 0
+      Rational(-1, 2).truncate.should == 0
+    end
+  end
+
+  describe "with an explicit precision = 0" do
+    it "returns an integer" do
+      @rational.truncate(0).should.is_a?(Integer)
+    end
+
+    it "returns the truncated value toward 0" do
+      @rational.truncate(0).should == 314
+      Rational(1, 2).truncate(0).should == 0
+      Rational(-1, 2).truncate(0).should == 0
+    end
+  end
+
+  describe "with a precision < 0" do
+    it "returns an integer" do
+      @rational.truncate(-2).should.is_a?(Integer)
+      @rational.truncate(-1).should.is_a?(Integer)
+    end
+
+    it "moves the truncation point n decimal places left" do
+      @rational.truncate(-3).should == 0
+      @rational.truncate(-2).should == 300
+      @rational.truncate(-1).should == 310
+    end
+  end
+
+  describe "with a precision > 0" do
+    it "returns a Rational" do
+      @rational.truncate(1).should.is_a?(Rational)
+      @rational.truncate(2).should.is_a?(Rational)
+    end
+
+    it "moves the truncation point n decimal places right" do
+      @rational.truncate(1).should == Rational(1571, 5)
+      @rational.truncate(2).should == Rational(7857, 25)
+      @rational.truncate(3).should == Rational(62857, 200)
+    end
+  end
+
+  describe "with an invalid value for precision" do
+    it "raises a TypeError" do
+      -> { @rational.truncate(nil) }.should.raise(TypeError, "not an integer")
+      -> { @rational.truncate(1.0) }.should.raise(TypeError, "not an integer")
+      -> { @rational.truncate('') }.should.raise(TypeError, "not an integer")
+    end
+
+    it "does not call to_int on the argument" do
+      object = Object.new
+      object.should_not_receive(:to_int)
+      -> { @rational.truncate(object) }.should.raise(TypeError, "not an integer")
+    end
+  end
+end