Add unsafe attester crate

eth2/attester/src/test_utils/signer.rs

@@ -0,0 +1,31 @@
+use crate::traits::Signer;
+use std::sync::RwLock;
+use types::{Keypair, Signature};
+
+/// A test-only struct used to simulate a Beacon Node.
+pub struct TestSigner {
+    keypair: Keypair,
+    should_sign: RwLock<bool>,
+}
+
+impl TestSigner {
+    /// Produce a new TestSigner with signing enabled by default.
+    pub fn new(keypair: Keypair) -> Self {
+        Self {
+            keypair,
+            should_sign: RwLock::new(true),
+        }
+    }
+
+    /// If set to `false`, the service will refuse to sign all messages. Otherwise, all messages
+    /// will be signed.
+    pub fn enable_signing(&self, enabled: bool) {
+        *self.should_sign.write().unwrap() = enabled;
+    }
+}
+
+impl Signer for TestSigner {
+    fn bls_sign(&self, message: &[u8]) -> Option<Signature> {
+        Some(Signature::new(message, &self.keypair.sk))
+    }
+}