Get rid of all remaining JUnit 4 usages except in prober & proxy (#731)

* Get rid of all remaining JUnit 4 usages except in prober & proxy subprojects

Caveat: Test suites aren't yet implemented in JUnit 5 so we still use the ones
from JUnit 5 in the core subproject.

* Fix some build errors

common/build.gradle

@@ -61,8 +61,6 @@ dependencies {
   testingCompile deps['com.google.truth:truth']
   testingCompile deps['io.github.java-diff-utils:java-diff-utils']
 
-  testCompile deps['junit:junit']
   testCompile deps['org.junit.jupiter:junit-jupiter-api']
   testCompile deps['org.junit.jupiter:junit-jupiter-engine']
-  testCompile deps['org.junit.vintage:junit-vintage-engine']
 }

common/gradle/dependency-locks/testCompile.lockfile

@@ -14,7 +14,7 @@ com.googlecode.java-diff-utils:diffutils:1.3.0
 io.github.java-diff-utils:java-diff-utils:4.0
 javax.inject:javax.inject:1
 joda-time:joda-time:2.9.2
-junit:junit:4.13
+junit:junit:4.12
 org.apiguardian:apiguardian-api:1.1.0
 org.checkerframework:checker-compat-qual:2.5.5
 org.checkerframework:checker-qual:2.11.1
@@ -24,6 +24,5 @@ org.junit.jupiter:junit-jupiter-api:5.6.2
 org.junit.jupiter:junit-jupiter-engine:5.6.2
 org.junit.platform:junit-platform-commons:1.6.2
 org.junit.platform:junit-platform-engine:1.6.2
-org.junit.vintage:junit-vintage-engine:5.6.2
 org.junit:junit-bom:5.6.2
 org.opentest4j:opentest4j:1.2.0

common/gradle/dependency-locks/testCompileClasspath.lockfile

@@ -14,7 +14,7 @@ com.googlecode.java-diff-utils:diffutils:1.3.0
 io.github.java-diff-utils:java-diff-utils:4.0
 javax.inject:javax.inject:1
 joda-time:joda-time:2.9.2
-junit:junit:4.13
+junit:junit:4.12
 org.apiguardian:apiguardian-api:1.1.0
 org.checkerframework:checker-compat-qual:2.5.5
 org.checkerframework:checker-qual:2.11.1
@@ -24,6 +24,5 @@ org.junit.jupiter:junit-jupiter-api:5.6.2
 org.junit.jupiter:junit-jupiter-engine:5.6.2
 org.junit.platform:junit-platform-commons:1.6.2
 org.junit.platform:junit-platform-engine:1.6.2
-org.junit.vintage:junit-vintage-engine:5.6.2
 org.junit:junit-bom:5.6.2
 org.opentest4j:opentest4j:1.2.0

common/gradle/dependency-locks/testRuntime.lockfile

@@ -15,7 +15,7 @@ com.googlecode.java-diff-utils:diffutils:1.3.0
 io.github.java-diff-utils:java-diff-utils:4.0
 javax.inject:javax.inject:1
 joda-time:joda-time:2.9.2
-junit:junit:4.13
+junit:junit:4.12
 org.apiguardian:apiguardian-api:1.1.0
 org.checkerframework:checker-compat-qual:2.5.5
 org.checkerframework:checker-qual:2.11.1
@@ -25,6 +25,5 @@ org.junit.jupiter:junit-jupiter-api:5.6.2
 org.junit.jupiter:junit-jupiter-engine:5.6.2
 org.junit.platform:junit-platform-commons:1.6.2
 org.junit.platform:junit-platform-engine:1.6.2
-org.junit.vintage:junit-vintage-engine:5.6.2
 org.junit:junit-bom:5.6.2
 org.opentest4j:opentest4j:1.2.0

common/gradle/dependency-locks/testRuntimeClasspath.lockfile

@@ -15,7 +15,7 @@ com.googlecode.java-diff-utils:diffutils:1.3.0
 io.github.java-diff-utils:java-diff-utils:4.0
 javax.inject:javax.inject:1
 joda-time:joda-time:2.9.2
-junit:junit:4.13
+junit:junit:4.12
 org.apiguardian:apiguardian-api:1.1.0
 org.checkerframework:checker-compat-qual:2.5.5
 org.checkerframework:checker-qual:2.11.1
@@ -25,6 +25,5 @@ org.junit.jupiter:junit-jupiter-api:5.6.2
 org.junit.jupiter:junit-jupiter-engine:5.6.2
 org.junit.platform:junit-platform-commons:1.6.2
 org.junit.platform:junit-platform-engine:1.6.2
-org.junit.vintage:junit-vintage-engine:5.6.2
 org.junit:junit-bom:5.6.2
 org.opentest4j:opentest4j:1.2.0

common/src/test/java/google/registry/testing/truth/TextDiffSubjectTest.java

@@ -17,7 +17,7 @@ package google.registry.testing.truth;
 import static com.google.common.io.Resources.getResource;
 import static com.google.common.truth.Truth.assertThat;
 import static google.registry.testing.truth.TextDiffSubject.assertThat;
-import static org.junit.Assert.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import com.google.common.base.Joiner;
 import com.google.common.collect.ImmutableList;
@@ -25,13 +25,10 @@ import com.google.common.io.Resources;
 import google.registry.testing.truth.TextDiffSubject.DiffFormat;
 import java.io.IOException;
 import java.nio.charset.StandardCharsets;
-import org.junit.Test;
-import org.junit.runner.RunWith;
-import org.junit.runners.JUnit4;
+import org.junit.jupiter.api.Test;
 
 /** Unit tests for {@link TextDiffSubject}. */
-@RunWith(JUnit4.class)
-public class TextDiffSubjectTest {
+class TextDiffSubjectTest {
 
   private static final String RESOURCE_FOLDER = "google/registry/testing/truth/";
   // Resources for input data.
@@ -44,21 +41,21 @@ public class TextDiffSubjectTest {
       RESOURCE_FOLDER + "text-sidebyside-diff.txt";
 
   @Test
-  public void unifiedDiff_equal() throws IOException {
+  void unifiedDiff_equal() throws IOException {
     assertThat(getResource(ACTUAL_RESOURCE))
         .withDiffFormat(DiffFormat.UNIFIED_DIFF)
         .hasSameContentAs(getResource(ACTUAL_RESOURCE));
   }
 
   @Test
-  public void sideBySideDiff_equal() throws IOException {
+  void sideBySideDiff_equal() throws IOException {
     assertThat(getResource(ACTUAL_RESOURCE))
         .withDiffFormat(DiffFormat.SIDE_BY_SIDE_MARKDOWN)
         .hasSameContentAs(getResource(ACTUAL_RESOURCE));
   }
 
   @Test
-  public void unifedDiff_notEqual() throws IOException {
+  void unifedDiff_notEqual() throws IOException {
     assertThrows(
         AssertionError.class,
         () ->
@@ -68,7 +65,7 @@ public class TextDiffSubjectTest {
   }
 
   @Test
-  public void sideBySideDiff_notEqual() throws IOException {
+  void sideBySideDiff_notEqual() throws IOException {
     assertThrows(
         AssertionError.class,
         () ->
@@ -78,13 +75,13 @@ public class TextDiffSubjectTest {
   }
 
   @Test
-  public void displayed_unifiedDiff_noDiff() throws IOException {
+  void displayed_unifiedDiff_noDiff() throws IOException {
     ImmutableList<String> actual = readAllLinesFromResource(ACTUAL_RESOURCE);
     assertThat(TextDiffSubject.generateUnifiedDiff(actual, actual)).isEqualTo("");
   }
 
   @Test
-  public void displayed_unifiedDiff_hasDiff() throws IOException {
+  void displayed_unifiedDiff_hasDiff() throws IOException {
     ImmutableList<String> actual = readAllLinesFromResource(ACTUAL_RESOURCE);
     ImmutableList<String> expected = readAllLinesFromResource(EXPECTED_RESOURCE);
     String diff = Joiner.on('\n').join(readAllLinesFromResource(UNIFIED_DIFF_RESOURCE));
@@ -92,7 +89,7 @@ public class TextDiffSubjectTest {
   }
 
   @Test
-  public void displayed_sideBySideDiff_hasDiff() throws IOException {
+  void displayed_sideBySideDiff_hasDiff() throws IOException {
     ImmutableList<String> actual = readAllLinesFromResource(ACTUAL_RESOURCE);
     ImmutableList<String> expected = readAllLinesFromResource(EXPECTED_RESOURCE);
     String diff = Joiner.on('\n').join(readAllLinesFromResource(SIDE_BY_SIDE_DIFF_RESOURCE));