1 files changed, 154 insertions, 0 deletions
diff --git a/spec/ruby/core/enumerable/one_spec.rb b/spec/ruby/core/enumerable/one_spec.rb
new file mode 100644
index 0000000000..cf966d4a9b
--- /dev/null
+++ b/spec/ruby/core/enumerable/one_spec.rb
@@ -0,0 +1,154 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Enumerable#one?" do
+  before :each do
+    @empty = EnumerableSpecs::Empty.new
+    @enum = EnumerableSpecs::Numerous.new
+    @enum1 = EnumerableSpecs::Numerous.new(0, 1, 2, -1)
+    @enum2 = EnumerableSpecs::Numerous.new(nil, false, true)
+  end
+
+  it "always returns false on empty enumeration" do
+    @empty.should_not.one?
+    @empty.one? { true }.should == false
+  end
+
+  it "raises an ArgumentError when more than 1 argument is provided" do
+    -> { @enum.one?(1, 2, 3) }.should.raise(ArgumentError)
+    -> { [].one?(1, 2, 3) }.should.raise(ArgumentError)
+    -> { {}.one?(1, 2, 3) }.should.raise(ArgumentError)
+  end
+
+  it "does not hide exceptions out of #each" do
+    -> {
+      EnumerableSpecs::ThrowingEach.new.one?
+    }.should.raise(RuntimeError)
+
+    -> {
+      EnumerableSpecs::ThrowingEach.new.one? { false }
+    }.should.raise(RuntimeError)
+  end
+
+  describe "with no block" do
+    it "returns true if only one element evaluates to true" do
+      [false, nil, true].one?.should == true
+    end
+
+    it "returns false if two elements evaluate to true" do
+      [false, :value, nil, true].one?.should == false
+    end
+
+    it "returns false if all elements evaluate to false" do
+      [false, nil, false].one?.should == false
+    end
+
+    it "gathers whole arrays as elements when each yields multiple" do
+      multi = EnumerableSpecs::YieldsMultiWithSingleTrue.new
+      multi.one?.should == false
+    end
+  end
+
+  describe "with a block" do
+    it "returns true if block returns true once" do
+      [:a, :b, :c].one? { |s| s == :a }.should == true
+    end
+
+    it "returns false if the block returns true more than once" do
+      [:a, :b, :c].one? { |s| s == :a || s == :b }.should == false
+    end
+
+    it "returns false if the block only returns false" do
+      [:a, :b, :c].one? { |s| s == :d }.should == false
+    end
+
+    it "does not hide exceptions out of the block" do
+      -> {
+        @enum.one? { raise "from block" }
+      }.should.raise(RuntimeError)
+    end
+
+    it "gathers initial args as elements when each yields multiple" do
+      multi = EnumerableSpecs::YieldsMulti.new
+      yielded = []
+      multi.one? { |e| yielded << e; false }.should == false
+      yielded.should == [1, 3, 6]
+    end
+
+    it "yields multiple arguments when each yields multiple" do
+      multi = EnumerableSpecs::YieldsMulti.new
+      yielded = []
+      multi.one? { |*args| yielded << args; false }.should == false
+      yielded.should == [[1, 2], [3, 4, 5], [6, 7, 8, 9]]
+    end
+  end
+
+  describe 'when given a pattern argument' do
+    it "calls `===` on the pattern the return value" do
+      pattern = EnumerableSpecs::Pattern.new { |x| x == 1 }
+      @enum1.one?(pattern).should == true
+      pattern.yielded.should == [[0], [1], [2], [-1]]
+    end
+
+    it "always returns false on empty enumeration" do
+      @empty.one?(Integer).should == false
+      [].one?(Integer).should == false
+      {}.one?(NilClass).should == false
+    end
+
+    it "does not hide exceptions out of #each" do
+      -> {
+        EnumerableSpecs::ThrowingEach.new.one?(Integer)
+      }.should.raise(RuntimeError)
+    end
+
+    it "returns true if the pattern returns a truthy value only once" do
+      @enum2.one?(NilClass).should == true
+      pattern = EnumerableSpecs::Pattern.new { |x| x == 2 }
+      @enum1.one?(pattern).should == true
+
+      [1, 2, 42, 3].one?(pattern).should == true
+
+      pattern = EnumerableSpecs::Pattern.new { |x| x == [:b, 2] }
+      {a: 1, b: 2}.one?(pattern).should == true
+    end
+
+    it "returns false if the pattern returns a truthy value more than once" do
+      pattern = EnumerableSpecs::Pattern.new { |x| !x }
+      @enum2.one?(pattern).should == false
+      pattern.yielded.should == [[nil], [false]]
+
+      [1, 2, 3].one?(Integer).should == false
+      {a: 1, b: 2}.one?(Array).should == false
+    end
+
+    it "returns false if the pattern never returns a truthy value" do
+      pattern = EnumerableSpecs::Pattern.new { |x| nil }
+      @enum1.one?(pattern).should == false
+      pattern.yielded.should == [[0], [1], [2], [-1]]
+
+      [1, 2, 3].one?(pattern).should == false
+      {a: 1}.one?(pattern).should == false
+    end
+
+    it "does not hide exceptions out of pattern#===" do
+      pattern = EnumerableSpecs::Pattern.new { raise "from pattern" }
+      -> {
+        @enum.one?(pattern)
+      }.should.raise(RuntimeError)
+    end
+
+    it "calls the pattern with gathered array when yielded with multiple arguments" do
+      multi = EnumerableSpecs::YieldsMulti.new
+      pattern = EnumerableSpecs::Pattern.new { false }
+      multi.one?(pattern).should == false
+      pattern.yielded.should == [[[1, 2]], [[3, 4, 5]], [[6, 7, 8, 9]]]
+    end
+
+    it "ignores the block if there is an argument" do
+      -> {
+        EnumerableSpecs::Numerous.new(1, 2, 3, 4, "5").one?(String) { false }.should == true
+      }.should complain(/given block not used/)
+    end
+  end
+end