Print message if no gas report to show

Author: ddoktorski

crates/forge-runner/src/gas/report.rs

@@ -109,6 +109,13 @@ impl ReportData {
 
 impl Display for ReportData {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        if self.0.is_empty() {
+            writeln!(
+                f,
+                "\nNo contract gas usage data to display. Make sure your test include transactions."
+            )?;
+        }
+
         for (name, contract_info) in &self.0 {
             if !contract_info.functions.is_empty() {
                 let table = format_table_output(contract_info, name);

crates/forge/tests/e2e/gas_report.rs

@@ -115,3 +115,30 @@ fn multiple_contracts_and_constructor() {
     "},
     );
 }
+
+#[test]
+fn no_transactions() {
+    let temp = setup_package("simple_package");
+    let output = test_runner(&temp)
+        .arg("--gas-report")
+        .arg("test_fib")
+        .assert()
+        .code(0);
+
+    assert_stdout_contains(
+        output,
+        indoc! {r"
+    [..]Compiling[..]
+    [..]Finished[..]
+
+
+    Collected 1 test(s) from simple_package package
+    Running 1 test(s) from src/
+    [PASS] simple_package::tests::test_fib (l1_gas: ~0, l1_data_gas: ~0, l2_gas: ~[..])
+    No contract gas usage data to display. Make sure your test include transactions.
+
+    Running 0 test(s) from tests/
+    Tests: 1 passed, 0 failed, 0 ignored, [..] filtered out
+    "},
+    );
+}