Wow. A clever solution indeed. Just never thought it this way. !!

Your arrayList grows too much. You should think of modifying your idea of a solution.
Try to debug in your IDE by printing the arrayList size with big enough numbers for length and width.

Do you get the same error when you recreate the test case locally in your IDE?

I'm having this java heap space error. What is causing this error and is there a solution for it?
I'm not sure if my code is necessary to solve the error so I'll only include the error message here for now.

Error message:
java.lang.OutOfMemoryError: Java heap space
at java.base/java.util.Arrays.copyOf(Arrays.java:3689)
at java.base/java.util.ArrayList.grow(ArrayList.java:237)
at java.base/java.util.ArrayList.grow(ArrayList.java:242)
at java.base/java.util.ArrayList.add(ArrayList.java:485)
at java.base/java.util.ArrayList.add(ArrayList.java:498)
at SqInRect.sqInRect(SqInRect.java:21)
at SqInRectTest.test(SqInRectTest.java:88)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at org.junit.runner.JUnitCore.run(JUnitCore.java:115)
at org.junit.vintage.engine.execution.RunnerExecutor.execute(RunnerExecutor.java:40)
at org.junit.vintage.engine.VintageTestEngine$$Lambda$212/0x00000008400d9c40.accept(Unknown Source)
at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:183)
at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:195)
at java.base/java.util.Iterator.forEachRemaining(Iterator.java:133)
at java.base/java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1801)

This was challenging considering the previous Kata's. Excited to see what's next.

Add a print statement to your function to print the input, and you get the inputs for the test-case :)