Add integration test for scyjava's heap functions

There are two classes of functions:

1. scyjava.config functions to instruct Java how much memory to use; and
2. scyjava._java functions to report back how much it is actually using.

This integration test uses both to validate that it all works properly.

Author: ctrueden

tests/it/java_heap.py

@@ -0,0 +1,34 @@
+"""
+Test scyjava JVM memory-related functions.
+"""
+
+import scyjava
+
+mb_initial = 50  # initial MB of memory to snarf up
+
+scyjava.config.set_heap_min(mb=mb_initial)
+scyjava.config.set_heap_max(gb=1)
+
+assert not scyjava.jvm_started()
+scyjava.start_jvm()
+
+assert scyjava.available_processors() >= 1
+
+mb_max = scyjava.memory_max() // 1024 // 1024
+mb_total = scyjava.memory_total() // 1024 // 1024
+mb_used = scyjava.memory_used() // 1024 // 1024
+
+# Used memory should be less than the current memory total,
+# which should be less than the maximum heap size.
+assert mb_used <= mb_total <= mb_max, f"{mb_used=} {mb_total=} {mb_max=}"
+
+# The maximum heap size should be approximately 1 GB.
+assert 900 <= mb_max <= 1024, f"{mb_max=}"
+
+# Most of that memory should still be free; i.e.,
+# we should not be using more than a few MB yet.
+assert mb_used <= 5, f"{mb_used=}"
+
+# The total MB available to Java at this moment
+# should be close to our requested initial amount.
+assert abs(mb_total - mb_initial) < 5, f"{mb_total=} {mb_initial=}"