Theo Weidmann f64f22b360 8346107: Generators: testing utility for random value generation
Co-authored-by: Emanuel Peter <epeter@openjdk.org>
Reviewed-by: epeter, chagedorn
2025-01-16 12:17:21 +00:00

82 lines
2.9 KiB
Java

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/*
* @test
* @summary An example test that shows how to use the Generators library.
* @modules java.base/jdk.internal.misc
* @library /test/lib /
* @run driver testlibrary_tests.generators.tests.ExampleTest
*/
package testlibrary_tests.generators.tests;
import compiler.lib.generators.Generator;
import static compiler.lib.generators.Generators.G;
public class ExampleTest {
static class FakeException extends RuntimeException {}
static class UnderTest {
private enum State { STAND_BY, FIRST, SECOND };
private State state = State.STAND_BY;
void doIt(int x) {
state = switch (state) {
case State.STAND_BY -> x == (1 << 10) + 3 ? State.FIRST : State.STAND_BY;
case State.FIRST -> x == (1 << 5) - 2 ? State.SECOND : State.STAND_BY;
case State.SECOND -> {
if (x == (1 << 4)) throw new FakeException();
yield State.STAND_BY;
}
};
}
}
public static void main(String[] args) {
// This test should print "Assertion triggered by special" (see the math below) but almost never
// "Assertion triggered by uniform" as the chance of triggering is about 2^-96.
try {
test(G.uniformInts());
} catch (FakeException e) {
System.out.println("Assertion triggered by uniform");
}
try {
// 408 ints => 1/408 * 1/408 * 1/408 => 1/67_917_312 => with 70_000_000 loop iterations we should trigger
test(G.powerOfTwoInts(3));
} catch (FakeException e) {
System.out.println("Assertion triggered by special");
}
}
public static void test(Generator<Integer> g) {
UnderTest underTest = new UnderTest();
for (int i = 0; i < 70_000_000 * 3; i++) {
underTest.doIt(g.next());
}
}
}