Fix fork choice in test runtime

Author: teor2345

Cargo.lock

@@ -33,3 +33,5 @@ std = [
     "subspace-kzg?/std",
     "thiserror/std"
 ]
+# Activate test APIs and workarounds
+testing = []

crates/subspace-verification/Cargo.toml

@@ -189,6 +189,15 @@ pub struct VerifySolutionParams {
 /// Calculate the block's contribution to the fork weight, which is derived from the provided
 /// solution range.
 pub fn calculate_block_fork_weight(solution_range: SolutionRange) -> BlockForkWeight {
+    // Work around the test runtime accepting all solutions, which causes blocks to have zero
+    // fork weight. This makes each node keep its own blocks, and never reorg to a common chain.
+    #[cfg(feature = "testing")]
+    let solution_range = if solution_range == SolutionRange::MAX {
+        SolutionRange::MAX - 1
+    } else {
+        solution_range
+    };
+
     BlockForkWeight::from(SolutionRange::MAX - solution_range)
 }
 

crates/subspace-verification/src/lib.rs

@@ -63,6 +63,8 @@ static_assertions.workspace = true
 subspace-core-primitives.workspace = true
 subspace-runtime-primitives.workspace = true
 subspace-test-primitives.workspace = true
+# Activate a testing workaround for the fork choice rule
+subspace-verification = { workspace = true, features = ["testing"] }
 
 [build-dependencies]
 substrate-wasm-builder = { workspace = true, optional = true }