1 files changed, 83 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..ee7f044905
--- /dev/null
+++ b/spec/ruby/core/string/delete_prefix_spec.rb
@@ -0,0 +1,83 @@
+# -*- encoding: utf-8 -*-
+# frozen_string_literal: false
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+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 "does not remove partial bytes, only full characters" do
+    "\xe3\x81\x82".delete_prefix("\xe3").should == "\xe3\x81\x82"
+  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 String instance when called on a subclass instance" do
+    s = StringSpecs::MyString.new('hello')
+    s.delete_prefix('hell').should be_an_instance_of(String)
+  end
+
+  it "returns a String in the same encoding as self" do
+    'hello'.encode("US-ASCII").delete_prefix('hell').encoding.should == Encoding::US_ASCII
+  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 FrozenError when self is frozen" do
+    -> { 'hello'.freeze.delete_prefix!('hell') }.should raise_error(FrozenError)
+    -> { 'hello'.freeze.delete_prefix!('') }.should raise_error(FrozenError)
+    -> { ''.freeze.delete_prefix!('') }.should raise_error(FrozenError)
+  end
+end