Add test_long_chain_with_restart_from_snapshot (#10193)

The main motivation for the test is to see how garbage collection will
behave without caches if we restart from the middle of an epoch.

integration-tests/src/tests/client/process_blocks.rs

@@ -3431,6 +3431,54 @@ fn test_catchup_no_sharding_change() {
     }
 }
 
+/// Run `gc_num_epochs_to_keep` epochs + several blocks.
+/// Start a second env from the "snapshot" of the first.
+/// Run one more epoch.
+/// "Restart from the snapshot" is to ensure that we can continue producing blocks without relying on caches.
+#[test]
+fn test_long_chain_with_restart_from_snapshot() {
+    init_test_logger();
+
+    let epoch_length = 25;
+
+    let mut genesis = Genesis::test(vec!["test0".parse().unwrap()], 1);
+
+    genesis.config.epoch_length = epoch_length;
+    let mut chain_genesis = ChainGenesis::test();
+    chain_genesis.epoch_length = epoch_length;
+    let mut env1 = TestEnv::builder(chain_genesis.clone())
+        .real_epoch_managers(&genesis.config)
+        .nightshade_runtimes(&genesis)
+        .archive(false)
+        .build();
+
+    // In TestEnv `gc_blocks_limit` defaults to 100.
+    // That means that whole epoch will be garbage collected in one block.
+    // We want this test to have "more realistic" snapshot setup, where last kept epoch is only partially garbage collected.
+    //
+    // `gc_blocks_limit = 2` is the default setup in production.
+    env1.clients[0].config.gc.gc_blocks_limit = 2;
+
+    let max_height = epoch_length * env1.clients[0].config.gc.gc_num_epochs_to_keep + 3;
+
+    for h in 1..max_height {
+        let block = env1.clients[0].produce_block(h).unwrap().unwrap();
+        env1.process_block(0, block.clone(), Provenance::PRODUCED);
+    }
+
+    let mut env2 = TestEnv::builder(chain_genesis)
+        .stores(vec![env1.clients[0].chain.store().store().clone()])
+        .real_epoch_managers(&genesis.config)
+        .nightshade_runtimes(&genesis)
+        .archive(false)
+        .build();
+
+    for h in max_height..(max_height + epoch_length) {
+        let block = env2.clients[0].produce_block(h).unwrap().unwrap();
+        env2.process_block(0, block.clone(), Provenance::PRODUCED);
+    }
+}
+
 /// These tests fail on aarch because the WasmtimeVM::precompile method doesn't populate the cache.
 mod contract_precompilation_tests {
     use super::*;