test: add tests for memory expansion on access

Removed a couple of tests for write beyond capacity.
This is because memory is now auto expanded during write.

packages/vm/tests/api/evm/memory.spec.ts

@@ -5,7 +5,6 @@ tape('Memory', (t) => {
   const m = new Memory()
   t.test('should have 0 capacity initially', (st) => {
     st.equal(m._store.length, 0)
-    st.throws(() => m.write(0, 3, Buffer.from([1, 2, 3])), /capacity/)
     st.end()
   })
 
@@ -25,11 +24,6 @@ tape('Memory', (t) => {
     st.end()
   })
 
-  t.test('should not write value beyond capacity', (st) => {
-    st.throws(() => m.write(30, 3, Buffer.from([1, 2, 3])), /capacity/)
-    st.end()
-  })
-
   t.test('should write value', (st) => {
     m.write(29, 3, Buffer.from([1, 2, 3]))
     st.ok(m.read(29, 5).equals(Buffer.from([1, 2, 3, 0, 0])))
@@ -40,4 +34,44 @@ tape('Memory', (t) => {
     st.throws(() => m.write(0, 5, Buffer.from([8, 8, 8])), /size/)
     st.end()
   })
+
+  t.test(
+    'should expand by word (32 bytes) properly when writing to previously untouched location',
+    (st) => {
+      const memory = new Memory()
+      memory.write(0, 1, Buffer.from([1]))
+      st.equal(memory._store.length, 32)
+
+      memory.write(1, 3, Buffer.from([2, 2, 2]))
+      st.equal(memory._store.length, 32)
+
+      memory.write(4, 32, Buffer.allocUnsafe(32).fill(3))
+      st.equal(memory._store.length, 64)
+
+      memory.write(36, 32, Buffer.allocUnsafe(32).fill(4))
+      st.equal(memory._store.length, 96)
+
+      st.end()
+    }
+  )
+
+  t.test('should expand by word (32 bytes) when reading a previously untouched location', (st) => {
+    const memory = new Memory()
+    memory.read(0, 8)
+    st.equal(memory._store.length, 32)
+
+    memory.read(1, 16)
+    st.equal(memory._store.length, 32)
+
+    memory.read(1, 32)
+    st.equal(memory._store.length, 64)
+
+    memory.read(32, 32)
+    st.equal(memory._store.length, 64)
+
+    memory.read(33, 32)
+    st.equal(memory._store.length, 96)
+
+    st.end()
+  })
 })