refactor: explain what we test and why

tests/trustless_gateway_car_test.go

@@ -617,9 +617,10 @@ func TestTrustlessCarEntityBytes(t *testing.T) {
 				),
 		},
 		{
-			Name: "GET CAR with entity-bytes requesting a range from the end of a file",
+			Name: "GET CAR with entity-bytes requesting a range from the end of a file that is bigger than a file itself",
 			Hint: `
-				The response MUST contain only the minimal set of blocks necessary for fulfilling the range request
+				The response MUST contain only the minimal set of blocks necessary for fulfilling the range request,
+				and requests for part beyond the start of a file are silently ignored.
 			`,
 			Request: Request().
 				Path("/ipfs/{{cid}}", subdirWithMixedBlockFiles.MustGetCidWithCodec(0x70, "subdir", "multiblock.txt")).
@@ -633,15 +634,20 @@ func TestTrustlessCarEntityBytes(t *testing.T) {
 						IgnoreRoots().
 						HasBlocks(
 							flattenStrings(t,
-								subdirWithMixedBlockFiles.MustGetCid("subdir", "multiblock.txt"),
-								subdirWithMixedBlockFiles.MustGetDescendantsCids("subdir", "multiblock.txt")[:len(subdirWithMixedBlockFiles.MustGetDescendantsCids("subdir", "multiblock.txt"))-1])...,
-						).
+								subdirWithMixedBlockFiles.MustGetCid("subdir", "multiblock.txt"), // dag-pb root of the file DAG
+								"bafkreie5noke3mb7hqxukzcy73nl23k6lxszxi5w3dtmuwz62wnvkpsscm",    // 256 chunk
+								"bafkreih4ephajybraj6wnxsbwjwa77fukurtpl7oj7t7pfq545duhot7cq",    // 256
+								"bafkreigu7buvm3cfunb35766dn7tmqyh2um62zcio63en2btvxuybgcpue",    // 256
+								"bafkreicll3huefkc3qnrzeony7zcfo7cr3nbx64hnxrqzsixpceg332fhe",    // 256
+								// and we dont expect the last chunk at "bafkreifst3pqztuvj57lycamoi7z34b4emf7gawxs74nwrc2c7jncmpaqm"
+								// because it has size of 2 and we did -3 from the end, so this one should be skipped
+							)...).
 						Exactly().
 						InThatOrder(),
 				),
 		},
 		{
-			Name: "GET CAR with entity-bytes requesting the first byte of a file",
+			Name: "GET CAR with entity-bytes requesting only the blocks for the first byte of a file",
 			Hint: `
 				The response MUST contain only the first block of the file.
 			`,
@@ -835,6 +841,7 @@ func TestTrustlessCarOrderAndDuplicates(t *testing.T) {
 	RunWithSpecs(t, tests, specs.TrustlessGatewayCAROptional)
 }
 
+// TODO: this feels like it could be an internal detail of HasBlocks
 func flattenStrings(t *testing.T, values ...interface{}) []string {
 	var res []string
 	for _, v := range values {