Make student test grading block optional

Author: jon-bell

dist/grader/types.d.ts

@@ -385,7 +385,7 @@ class Grader {
         mutantResults = await this.builder.mutationTest()
       }
     } else if (
-      this.config.build.student_tests.grading ===
+      this.config.build.student_tests?.grading ===
         'student-impl-coverage-report-only' &&
       this.config.submissionFiles.testFiles.length > 0
     ) {
@@ -411,7 +411,7 @@ class Grader {
     const expectedArtifacts = this.config.build.artifacts || []
 
     if (
-      this.config.build.student_tests.grading ===
+      this.config.build.student_tests?.grading ===
       'student-impl-coverage-report-only'
     ) {
       const passingTestCount = studentTestResults?.filter(

dist/index.js

@@ -9,7 +9,7 @@ export interface BuildConfig {
     preset: 'checkstyle'
     policy: 'fail' | 'warn' | 'ignore'
   }
-  student_tests: {
+  student_tests?: {
     grading: 'none' | 'mutation' | 'student-impl-coverage-report-only'
   }
 }