Add docs/comments explaining unit tests

nano/core_test/node.cpp

@@ -4298,6 +4298,8 @@ TEST (rep_crawler, local)
 }
 }
 
+// Test that a node configured with `enable_pruning` and `max_pruning_age = 1s` will automatically
+// prune old confirmed blocks without explicitly saying `node.ledger_pruning` in the unit test
 TEST (node, pruning_automatic)
 {
 	nano::system system{};
@@ -4352,6 +4354,8 @@ TEST (node, pruning_automatic)
 	ASSERT_TRUE (node1.ledger.block_or_pruned_exists (send2->hash ()));
 }
 
+// Test that a node configured with `enable_pruning` will
+// prune OLD-enough confirmed blocks by explicitly saying `node.ledger_pruning` in the unit test
 TEST (node, pruning_age)
 {
 	nano::system system{};
@@ -4413,6 +4417,8 @@ TEST (node, pruning_age)
 	ASSERT_TRUE (node1.ledger.block_or_pruned_exists (send2->hash ()));
 }
 
+// Test that a node configured with `enable_pruning` will
+// prune DEEP-enough confirmed blocks by explicitly saying `node.ledger_pruning` in the unit test
 TEST (node, pruning_depth)
 {
 	nano::system system{};