[MINOR][TESTS] Replace JVM assert with JUnit Assert in tests

[srowen]

What changes were proposed in this pull request?

Use JUnit assertions in tests uniformly, not JVM assert() statements.

Why are the changes needed?

assert() statements do not produce as useful errors when they fail, and, if they were somehow disabled, would fail to test anything.

Does this PR introduce any user-facing change?

No. The assertion logic should be identical.

How was this patch tested?

Existing tests.

[dongjoon-hyun]

Is this all? It seems that we have more instances.

[srowen]

That's all IntelliJ found in the Java test code. There may be some in non-test code, but some are possibly legitimate. There are, I think, cases where assert() is used for argument checking in non-test code and that's not really what it's for, but a separate thing.

Yeah there are some in Scala tests too, I'll fix those. They're not obvious as scalatest uses assert() too, but we can look for use of scala.Predef.assert()

[SparkQA]

Test build #114032 has finished for PR 26581 at commit e0c572b.

• This patch fails to build.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #114027 has finished for PR 26581 at commit 2219d2e.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[srowen]

(PS to be clear the latest test failed; its result just came first. I'll investigate)

[dongjoon-hyun]

It seems that both Jenkins/GitHubAction fails due to scala.reflect.macros.TypecheckException: not found: value assertionsHelper.

[error] /home/jenkins/workspace/SparkPullRequestBuilder/core/src/test/scala/org/apache/spark/executor/ExecutorSuite.scala:570: exception during macro expansion: 
[error] scala.reflect.macros.TypecheckException: not found: value assertionsHelper
[error] 	at scala.reflect.macros.contexts.Typers.$anonfun$typecheck$3(Typers.scala:44)
[error] 	at scala.reflect.macros.contexts.Typers.$anonfun$typecheck$2(Typers.scala:38)
[error] 	at scala.reflect.macros.contexts.Typers.doTypecheck$1(Typers.scala:37)
[error] 	at scala.reflect.macros.contexts.Typers.$anonfun$typecheck$7(Typers.scala:50)
[error] 	at scala.reflect.internal.Trees.wrappingIntoTerm(Trees.scala:1756)
[error] 	at scala.reflect.internal.Trees.wrappingIntoTerm$(Trees.scala:1753)
[error] 	at scala.reflect.internal.SymbolTable.wrappingIntoTerm(SymbolTable.scala:28)
[error] 	at scala.reflect.macros.contexts.Typers.typecheck(Typers.scala:50)
[error] 	at scala.reflect.macros.contexts.Typers.typecheck$(Typers.scala:32)
[error] 	at scala.reflect.macros.contexts.Context.typecheck(Context.scala:18)
[error] 	at scala.reflect.macros.contexts.Context.typecheck(Context.scala:18)
[error] 	at scala.reflect.macros.Typers.typeCheck(Typers.scala:70)
[error] 	at scala.reflect.macros.Typers.typeCheck$(Typers.scala:69)
[error] 	at scala.reflect.macros.contexts.Context.typeCheck(Context.scala:18)
[error] 	at org.scalactic.MacroOwnerRepair.repairOwners(MacroOwnerRepair.scala:35)
[error] 	at org.scalactic.BooleanMacro.genMacro(BooleanMacro.scala:837)
[error] 	at org.scalatest.AssertionsMacro$.assert(AssertionsMacro.scala:34)
[error] 	at sun.reflect.GeneratedMethodAccessor19.invoke(Unknown Source)
[error] 	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[error] 	at java.lang.reflect.Method.invoke(Method.java:498)
[error] 	at scala.reflect.macros.runtime.JavaReflectionRuntimes$JavaReflectionResolvers.$anonfun$resolveJavaReflectionRuntime$6(JavaReflectionRuntimes.scala:51)
[error] 	at scala.tools.nsc.typechecker.Macros.macroExpandWithRuntime(Macros.scala:824)
[error]           Assertions.assert(TaskContext.get().asInstanceOf[TaskContextImpl].fetchFailed.isDefined)
[error]                            ^

[SparkQA]

Test build #114040 has finished for PR 26581 at commit 90fd917.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[HyukjinKwon]

retest this please

[SparkQA]

Test build #114056 has finished for PR 26581 at commit 90fd917.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[srowen]

PS @dongjoon-hyun is this failure 'normal'?

https://github.com/apache/spark/runs/311900764

gzip: stdin: unexpected end of file
tar: Child returned status 1
tar: Error is not recoverable: exiting now
Using `mvn` from path: /home/runner/work/spark/spark/build/apache-maven-3.6.2/bin/mvn
./build/mvn: line 172: /home/runner/work/spark/spark/build/apache-maven-3.6.2/bin/mvn: No such file or directory

Just can't download maven?

[SparkQA]

Test build #114167 has finished for PR 26581 at commit a5b6e9e.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[dongjoon-hyun]

Yes. It's a normal Maven Download failure. I'll try to cache the maven directory, too. Thanks!

[SparkQA]

Test build #114174 has finished for PR 26581 at commit a599dd6.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[srowen]

Merged to master