1 files changed, 81 insertions, 0 deletions
diff --git a/spec/ruby/core/string/delete_prefix_spec.rb b/spec/ruby/core/string/delete_prefix_spec.rb
new file mode 100644
index 0000000000..94d486eace
--- /dev/null
+++ b/spec/ruby/core/string/delete_prefix_spec.rb
@@ -0,0 +1,81 @@
+# -*- encoding: utf-8 -*-
+require File.expand_path('../../../spec_helper', __FILE__)
+require File.expand_path('../fixtures/classes.rb', __FILE__)
+
+ruby_version_is '2.5' do
+  describe "String#delete_prefix" do
+    it "returns a copy of the string, with the given prefix removed" do
+      'hello'.delete_prefix('hell').should == 'o'
+      'hello'.delete_prefix('hello').should == ''
+    end
+
+    it "returns a copy of the string, when the prefix isn't found" do
+      s = 'hello'
+      r = s.delete_prefix('hello!')
+      r.should_not equal s
+      r.should == s
+      r = s.delete_prefix('ell')
+      r.should_not equal s
+      r.should == s
+      r = s.delete_prefix('')
+      r.should_not equal s
+      r.should == s
+    end
+
+    it "taints resulting strings when other is tainted" do
+      'hello'.taint.delete_prefix('hell').tainted?.should == true
+      'hello'.taint.delete_prefix('').tainted?.should == true
+    end
+
+    it "doesn't set $~" do
+      $~ = nil
+
+      'hello'.delete_prefix('hell')
+      $~.should == nil
+    end
+
+    it "calls to_str on its argument" do
+      o = mock('x')
+      o.should_receive(:to_str).and_return 'hell'
+      'hello'.delete_prefix(o).should == 'o'
+    end
+
+    it "returns a subclass instance when called on a subclass instance" do
+      s = StringSpecs::MyString.new('hello')
+      s.delete_prefix('hell').should be_an_instance_of(StringSpecs::MyString)
+    end
+  end
+
+  describe "String#delete_prefix!" do
+    it "removes the found prefix" do
+      s = 'hello'
+      s.delete_prefix!('hell').should equal(s)
+      s.should == 'o'
+    end
+
+    it "returns nil if no change is made" do
+      s = 'hello'
+      s.delete_prefix!('ell').should == nil
+      s.delete_prefix!('').should == nil
+    end
+
+    it "doesn't set $~" do
+      $~ = nil
+
+      'hello'.delete_prefix!('hell')
+      $~.should == nil
+    end
+
+    it "calls to_str on its argument" do
+      o = mock('x')
+      o.should_receive(:to_str).and_return 'hell'
+      'hello'.delete_prefix!(o).should == 'o'
+    end
+
+    it "raises a RuntimeError when self is frozen" do
+      lambda { 'hello'.freeze.delete_prefix!('hell') }.should raise_error(RuntimeError)
+      lambda { 'hello'.freeze.delete_prefix!('') }.should raise_error(RuntimeError)
+      lambda { ''.freeze.delete_prefix!('') }.should raise_error(RuntimeError)
+    end
+  end
+end