Add rake coverage

Author: jvmvik

README.md

@@ -1128,7 +1128,7 @@ This project source code and coding style was inspired by the most awesome Ruby
 ### Code quality expectations
  - 0 lint offense: `rake lint`
  - 100% tests passing: `rake test`
- - 100% code coverage: `rake test` (simple-cov)
+ - 100% code coverage: `rake coverage` (simple-cov)
 
 # Developer Guide
 ## Design : UML diagram
@@ -1205,8 +1205,14 @@ Run basic test
 $ rake test
 ```
 
-Review coverage report generated by `rake test`
+Run tests with code coverage
+```bash
+$ rake coverage
+```
+
+Review coverage report generated by `rake coverage`
 ```sh
+# Current coverage: 98.68% (75 / 76 lines)
 open coverage/index.html
 ```
 

README.md.erb

@@ -609,7 +609,7 @@ This project source code and coding style was inspired by the most awesome Ruby
 ### Code quality expectations
  - 0 lint offense: `rake lint`
  - 100% tests passing: `rake test`
- - 100% code coverage: `rake test` (simple-cov)
+ - 100% code coverage: `rake coverage` (simple-cov)
 
 # Developer Guide
 ## Design : UML diagram
@@ -686,8 +686,14 @@ Run basic test
 $ rake test
 ```
 
-Review coverage report generated by `rake test`
+Run tests with code coverage
+```bash
+$ rake coverage
+```
+
+Review coverage report generated by `rake coverage`
 ```sh
+# Current coverage: 98.68% (75 / 76 lines)
 open coverage/index.html
 ```
 

Rakefile

@@ -37,6 +37,12 @@ RSpec::Core::RakeTask.new(:test) do |t|
   t.rspec_opts = '--format documentation'
 end
 
+desc 'run tests under spec/serpapi/client/ with coverage'
+RSpec::Core::RakeTask.new(:coverage) do |t|
+  t.pattern = Dir.glob('spec/serpapi/client/*_spec.rb')
+  t.rspec_opts = '--format documentation'
+end
+
 desc 'validate all the examples (comprehensive set of tests)' 
 RSpec::Core::RakeTask.new(:regression) do |t|
   t.pattern = Dir.glob('spec/serpapi/client/example/*_spec.rb')