Running the JUnit tests from your IDE (probably built-in).
Calling ExprTest.main() (which just "manually" makes the calls that JUnit would).
If you get a compile-time error about “class junit.framework.TestCase not found”,
you'll need to make sure
(a) you have JUnit .jars downloaded, and
(b) your CLASSPATH includes it.
See how to run JUnit for further instructions.
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