README.md in salesforce_id-1.2.0 vs README.md in salesforce_id-1.3.0

@@ -88,9 +88,74 @@
 
 # Special feature, for even shorter ID creation
 SalesforceId("003G000001SUbc4") == SalesforceId.id("003G000001SUbc4") # => true
 ```
 
+### Test utilities
+
+#### SalesforceId::Random
+
+A useful utility class to generate random salesforce IDs
+
+```ruby
+# Generate a valid case-sensitive salesforce id
+SalesforceId::Random.sensitive # => 003G000001SUbc4
+
+# Generate a valid case-insensitive salesforce id
+SalesforceId::Random.insensitive # => 003G000001SUbc4IAD
+
+# Generate an **invalid** case-sensitive salesforce id
+SalesforceId::Random.invalid_sensitive # => 003G0-0001SUbc4
+
+# Generate a **invalid** case-insensitive salesforce id where the first 15
+# characters are invalid, not the checksum part
+SalesforceId::Random.insensitive # => 003-000001SUbc4IAD
+
+# Generate a **invalid** case-insensitive salesforce id where only the checksum
+# part (last 3 characters) is invalid
+SalesforceId::Random.insensitive # => 003G000001SUbc4I9D
+
+# Generate a valid SalesforceId::Safe salesforce id
+SalesforceId::Random.safe # => #<SalesforceId::Safe:0x007f86f2294c50 @value="003G000001SUbc4IAD">
+
+# Shorter version to perform `SalesforceId::Random.safe`
+SalesforceId.random # => #<SalesforceId::Safe:0x007f86f2294c50 @value="003G000001SUbc4IAD">
+```
+
+#### RSpec matchers
+
+Include `SalesforceId::RSpec` in your tests to get a bunch of salesforce id
+matchers
+
+```ruby
+RSpec.describe SalesforceId("003G000001SUbc4") do
+  include ::SalesforceId::RSpec
+  
+  it "is a sensitive salesforce id" do
+    expect(subject.to_sensitive).to be_sensitive_salesforce_id # => true
+  end
+  
+  it "is an insensitive salesforce id" do
+    expect(subject.to_insensitive).to be_insensitive_salesforce_id # => true
+  end
+
+  it "is a salesforce id" do
+    is_expected.to be_salesforce_id # => true
+  end
+
+  it "is a salesforce id in safe format (case-sensitive + checksum)" do
+    is_expected.to be_safe_salesforce_id # => true
+  end
+
+end
+```
+
+These tests will pass. Matchers will work with any object that can be converted
+into a string with `to_s`, including `SalesforceId::Safe`.
+
+One note on `be_safe_salesforce_id` matcher, it will consider safe **even
+strings** if they are of the correct format (case sensitive + checksum)
+
 ## Documentation
 
 Methods are documented in [salesforce_id_ext.h](https://github.com/Fire-Dragon-DoL/salesforce_id/blob/master/ext/salesforce_id/salesforce_id_ext.h), this file is
 the only public API of the gem, everything else must be considered private.