graph: Implement mock methods for MockBlock

graph/src/blockchain/mock.rs

@@ -48,15 +48,32 @@ pub struct MockBlock {
 
 impl Block for MockBlock {
     fn ptr(&self) -> BlockPtr {
-        todo!()
+        test_ptr(self.number as i32)
     }
 
     fn parent_ptr(&self) -> Option<BlockPtr> {
-        todo!()
+        if self.number == 0 {
+            None
+        } else {
+            Some(test_ptr(self.number as i32 - 1))
+        }
     }
 
     fn timestamp(&self) -> BlockTime {
-        todo!()
+        BlockTime::for_test(&self.ptr())
+    }
+}
+
+pub fn test_ptr(n: BlockNumber) -> BlockPtr {
+    test_ptr_reorged(n, 0)
+}
+
+pub fn test_ptr_reorged(n: BlockNumber, reorg_n: u32) -> BlockPtr {
+    let mut hash = H256::from_low_u64_be(n as u64);
+    hash[0..4].copy_from_slice(&reorg_n.to_be_bytes());
+    BlockPtr {
+        hash: hash.into(),
+        number: n,
     }
 }