diff --git a/foundry.toml b/foundry.toml
index f9679ee6..c873eaa4 100644
--- a/foundry.toml
+++ b/foundry.toml
@@ -3,7 +3,7 @@ fs_permissions = [{ access = "read-write", path = "./"}]
 
 [rpc_endpoints]
 # The RPC URLs are modified versions of the default for testing initialization.
-mainnet = "https://mainnet.infura.io/v3/b1d3925804e74152b316ca7da97060d3" # Different API key.
+mainnet = "https://eth-mainnet.alchemyapi.io/v2/WV407BEiBmjNJfKo9Uo_55u0z0ITyCOX" # Different API key.
 optimism_goerli = "https://goerli.optimism.io/" # Adds a trailing slash.
 arbitrum_one_goerli = "https://goerli-rollup.arbitrum.io/rpc/" # Adds a trailing slash.
 needs_undefined_env_var = "${UNDEFINED_RPC_URL_PLACEHOLDER}"
diff --git a/src/StdChains.sol b/src/StdChains.sol
index 0e8e4351..27e1bf25 100644
--- a/src/StdChains.sol
+++ b/src/StdChains.sol
@@ -197,7 +197,7 @@ abstract contract StdChains {
         // If adding an RPC here, make sure to test the default RPC URL in `testRpcs`
         setChainWithDefaultRpcUrl("anvil", ChainData("Anvil", 31337, "http://127.0.0.1:8545"));
         setChainWithDefaultRpcUrl(
-            "mainnet", ChainData("Mainnet", 1, "https://mainnet.infura.io/v3/b9794ad1ddf84dfb8c34d6bb5dca2001")
+            "mainnet", ChainData("Mainnet", 1, "https://eth-mainnet.alchemyapi.io/v2/pwc5rmJhrdoaSEfimoKEmsvOjKSmPDrP")
         );
         setChainWithDefaultRpcUrl(
             "goerli", ChainData("Goerli", 5, "https://goerli.infura.io/v3/b9794ad1ddf84dfb8c34d6bb5dca2001")
diff --git a/src/Test.sol b/src/Test.sol
index 9c7cbd68..5ff60ea3 100644
--- a/src/Test.sol
+++ b/src/Test.sol
@@ -27,4 +27,7 @@ import {Vm} from "./Vm.sol";
 import {TestBase} from "./Base.sol";
 
 // ⭐️ TEST
-abstract contract Test is TestBase, StdAssertions, StdChains, StdCheats, StdInvariant, StdUtils {}
+abstract contract Test is TestBase, StdAssertions, StdChains, StdCheats, StdInvariant, StdUtils {
+    // Note: IS_TEST() must return true.
+    bool public IS_TEST = true;
+}
diff --git a/test/StdChains.t.sol b/test/StdChains.t.sol
index 9a8f238b..4c3283a7 100644
--- a/test/StdChains.t.sol
+++ b/test/StdChains.t.sol
@@ -24,7 +24,7 @@ contract StdChainsMock is Test {
 contract StdChainsTest is Test {
     function test_ChainRpcInitialization() public {
         // RPCs specified in `foundry.toml` should be updated.
-        assertEq(getChain(1).rpcUrl, "https://mainnet.infura.io/v3/b1d3925804e74152b316ca7da97060d3");
+        assertEq(getChain(1).rpcUrl, "https://eth-mainnet.alchemyapi.io/v2/WV407BEiBmjNJfKo9Uo_55u0z0ITyCOX");
         assertEq(getChain("optimism_goerli").rpcUrl, "https://goerli.optimism.io/");
         assertEq(getChain("arbitrum_one_goerli").rpcUrl, "https://goerli-rollup.arbitrum.io/rpc/");
 
@@ -36,7 +36,7 @@ contract StdChainsTest is Test {
 
         // Cannot override RPCs defined in `foundry.toml`
         vm.setEnv("MAINNET_RPC_URL", "myoverride2");
-        assertEq(getChain("mainnet").rpcUrl, "https://mainnet.infura.io/v3/b1d3925804e74152b316ca7da97060d3");
+        assertEq(getChain("mainnet").rpcUrl, "https://eth-mainnet.alchemyapi.io/v2/WV407BEiBmjNJfKo9Uo_55u0z0ITyCOX");
 
         // Other RPCs should remain unchanged.
         assertEq(getChain(31337).rpcUrl, "http://127.0.0.1:8545");