fix: add Maybe BalanceAt expectations to prevent race with testify reflect

Tests using mock eth clients that don't set a BalanceAt expectation are
vulnerable to a data race: the balance monitor's background worker may
call BalanceAt during shutdown, hitting testify's unexpected-call error
path which does fmt.Sprintf("%#v", ctx) — an unsynchronized reflect read
that races with concurrent context cancellation.

Adding .Maybe().Return(big.NewInt(0), nil) registers the expectation so
testify takes the happy path (match and return) instead of the error
path (reflect into arguments). The race cannot fire on the happy path.

Author: Fletch153

core/internal/features/features_test.go

@@ -86,6 +86,7 @@ func TestIntegration_ExternalInitiatorV2(t *testing.T) {
 
 	ctx := testutils.Context(t)
 	ethClient := cltest.NewEthMocksWithStartupAssertions(t)
+	ethClient.On("BalanceAt", mock.Anything, mock.Anything, mock.Anything).Maybe().Return(big.NewInt(0), nil)
 
 	cfg := configtest.NewGeneralConfig(t, func(c *chainlink.Config, s *chainlink.Secrets) {
 		c.JobPipeline.ExternalInitiatorsEnabled = ptr(true)

core/services/job/runner_integration_test.go

@@ -784,6 +784,7 @@ func TestRunner_Success_Callback_AsyncJob(t *testing.T) {
 	t.Parallel()
 
 	ethClient := cltest.NewEthMocksWithStartupAssertions(t)
+	ethClient.On("BalanceAt", mock.Anything, mock.Anything, mock.Anything).Maybe().Return(big.NewInt(0), nil)
 
 	cfg := configtest.NewGeneralConfig(t, func(c *chainlink.Config, s *chainlink.Secrets) {
 		t := true
@@ -963,6 +964,7 @@ func TestRunner_Error_Callback_AsyncJob(t *testing.T) {
 	t.Parallel()
 
 	ethClient := cltest.NewEthMocksWithStartupAssertions(t)
+	ethClient.On("BalanceAt", mock.Anything, mock.Anything, mock.Anything).Maybe().Return(big.NewInt(0), nil)
 
 	cfg := configtest.NewGeneralConfig(t, func(c *chainlink.Config, s *chainlink.Secrets) {
 		t := true

core/services/pipeline/task.eth_call_test.go

@@ -297,6 +297,7 @@ func TestETHCallTask(t *testing.T) {
 			}
 
 			ethClient := clienttest.NewClient(t)
+			ethClient.On("BalanceAt", mock.Anything, mock.Anything, mock.Anything).Maybe().Return(big.NewInt(0), nil)
 			config := pipelinemocks.NewConfig(t)
 			test.setupClientMocks(ethClient, config)
 

core/services/relay/evm/write_target_test.go

@@ -125,6 +125,7 @@ func TestEvmWrite(t *testing.T) {
 	ht.On("LatestAndFinalizedBlock", mock.Anything).Return(&evmtypes.Head{Number: 99}, &evmtypes.Head{}, nil)
 	chain.On("HeadTracker").Return(ht)
 
+	evmClient.On("BalanceAt", mock.Anything, mock.Anything, mock.Anything).Maybe().Return(big.NewInt(0), nil)
 	chain.On("Client").Return(evmClient)
 
 	evmCfg := configtest.NewChainScopedConfig(t, func(c *toml.EVMConfig) {

core/services/vrf/v2/integration_v2_test.go

@@ -2129,6 +2129,7 @@ func TestStartingCountsV1(t *testing.T) {
 	ec.On("Dial", mock.Anything).Maybe().Return(nil)
 	ec.On("Close").Maybe().Return(nil)
 	ec.On("ConfiguredChainID").Return(testutils.SimulatedChainID)
+	ec.On("BalanceAt", mock.Anything, mock.Anything, mock.Anything).Maybe().Return(big.NewInt(0), nil)
 	ec.On("LatestBlockHeight", mock.Anything).Return(big.NewInt(2), nil).Maybe()
 	txm := makeTestTxm(t, txStore, ks.Eth(), ec)
 	legacyChains := evmtest.NewLegacyChains(t, evmtest.TestChainOpts{

core/web/pipeline_runs_controller_test.go

@@ -3,6 +3,7 @@ package web_test
 import (
 	"encoding/json"
 	"fmt"
+	"math/big"
 	"io"
 	"net/http"
 	"net/url"
@@ -36,6 +37,7 @@ func TestPipelineRunsController_CreateWithBody_HappyPath(t *testing.T) {
 
 	ctx := testutils.Context(t)
 	ethClient := cltest.NewEthMocksWithStartupAssertions(t)
+	ethClient.On("BalanceAt", mock.Anything, mock.Anything, mock.Anything).Maybe().Return(big.NewInt(0), nil)
 	cfg := configtest.NewGeneralConfig(t, func(c *chainlink.Config, s *chainlink.Secrets) {
 		c.JobPipeline.HTTPRequest.DefaultTimeout = commonconfig.MustNewDuration(2 * time.Second)
 		c.Database.Listener.FallbackPollInterval = commonconfig.MustNewDuration(10 * time.Millisecond)
@@ -92,6 +94,7 @@ func TestPipelineRunsController_CreateNoBody_HappyPath(t *testing.T) {
 
 	ctx := testutils.Context(t)
 	ethClient := cltest.NewEthMocksWithStartupAssertions(t)
+	ethClient.On("BalanceAt", mock.Anything, mock.Anything, mock.Anything).Maybe().Return(big.NewInt(0), nil)
 	cfg := configtest.NewGeneralConfig(t, func(c *chainlink.Config, s *chainlink.Secrets) {
 		c.JobPipeline.HTTPRequest.DefaultTimeout = commonconfig.MustNewDuration(2 * time.Second)
 		c.Database.Listener.FallbackPollInterval = commonconfig.MustNewDuration(10 * time.Millisecond)