chore: adjust code coverage percentage required

lesson_15/README.md

@@ -14,7 +14,7 @@ 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 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`.
+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 80% 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.
 

lesson_15/tdd/tdd_app/build.gradle.kts

@@ -49,6 +49,19 @@ tasks.jacocoTestReport {
   }
 }
 
+tasks.jacocoTestCoverageVerification {
+  violationRules {
+    rule {
+      limit {
+        minimum = "0.8".toBigDecimal()
+      }
+    }
+  }
+}
+
+tasks.check {
+	dependsOn(tasks.jacocoTestCoverageVerification)
+}
 
 configure<com.diffplug.gradle.spotless.SpotlessExtension> {