docs: update documentation:

Signed-off-by: Anthony D. Mays <[email protected]>

Author: anthonydmays

lesson_15/README.md

@@ -14,8 +14,9 @@ Please review the following resources before lecture:
 
 ### Unit Testing
 
-For the code in the Lesson 15 app, you will write tests in the [unit tests project][unit-tests-link]. You must write *at least* 5 tests for each of the `Employee` and `EmployeeManager` classes (10 tests minimum). Each class must have it's own corresponding test file.
+For the code in the Lesson 15 app, you will write tests in the [unit tests project][unit-tests-link]. You must achieve a code coverage of 90% or more. The coverage report can be viewed at [./tdd/tdd_app/build/reports/jacoco/test/html/index.html][coverage-report] after running `./gradlew check` or `./gradlew jacocoTestReport`.
 
 In addition to writing unit tests, you will need to implement a new method on the `Employee` class called `getDetails` that returns a string describing the employee using the Test-Driven Development methodology.
 
+[coverage-report]: ./tdd/tdd_app/build/reports/jacoco/test/html/index.html
 [unit-tests-link]: ./tdd/tdd_app/src/test/java/com/codedifferently/lesson15/