chainfee: use proper mock for WebAPIFeeSource in tests

lnwallet/chainfee/estimator_test.go

@@ -9,15 +9,6 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
-type mockSparseConfFeeSource struct {
-	url  string
-	fees map[uint32]uint32
-}
-
-func (e mockSparseConfFeeSource) GetFeeMap() (map[uint32]uint32, error) {
-	return e.fees, nil
-}
-
 // TestFeeRateTypes checks that converting fee rates between the
 // different types that represent fee rates and calculating fees
 // work as expected.
@@ -204,10 +195,9 @@ func TestWebAPIFeeEstimator(t *testing.T) {
 		maxTarget: minFeeRate,
 	}
 
-	feeSource := mockSparseConfFeeSource{
+	// Create a mock fee source and mock its returned map.
-		url:  "https://www.github.com",
+	feeSource := &mockFeeSource{}
-		fees: feeRateResp,
+	feeSource.On("GetFeeMap").Return(feeRateResp, nil)
-	}
 
 	estimator := NewWebAPIEstimator(feeSource, false)
 
@@ -238,12 +228,15 @@ func TestWebAPIFeeEstimator(t *testing.T) {
 
 			exp := SatPerKVByte(tc.expectedFeeRate).FeePerKWeight()
 			require.Equalf(t, exp, est, "target %v failed, fee "+
-				"map is %v", tc.target, feeSource.fees)
+				"map is %v", tc.target, feeRateResp)
 		})
 	}
 
 	// Stop the estimator when test ends.
 	require.NoError(t, estimator.Stop(), "unable to stop fee estimator")
+
+	// Assert the mocked fee source is called as expected.
+	feeSource.AssertExpectations(t)
 }
 
 // TestGetCachedFee checks that the fee caching logic works as expected.

lnwallet/chainfee/mocks.go

@@ -0,0 +1,17 @@
+package chainfee
+
+import "github.com/stretchr/testify/mock"
+
+type mockFeeSource struct {
+	mock.Mock
+}
+
+// A compile-time assertion to ensure that mockFeeSource implements the
+// WebAPIFeeSource interface.
+var _ WebAPIFeeSource = (*mockFeeSource)(nil)
+
+func (m *mockFeeSource) GetFeeMap() (map[uint32]uint32, error) {
+	args := m.Called()
+
+	return args.Get(0).(map[uint32]uint32), args.Error(1)
+}