chore: write tests for ArchivalNetworkEvent (#1329)

My aim here is to have marshal/unmarshal tests for all the toplevel data
structures inside the internal/model/archival.go file.

Once I have done that, I can have additional confidence about changing
the structure fields and simplifying the code.

All of this is preparatory work to automatically scrub HTTP measurements
which is something we should really do before continuing to improve the
boostrap process in light of ooni/probe#2531.

internal/model/archival_test.go

@@ -1768,5 +1768,176 @@ func TestArchivalHTTPRequestResult(t *testing.T) {
 
 // This test ensures that ArchivalNetworkEvent is WAI
 func TestArchivalNetworkEvent(t *testing.T) {
-	t.Skip("not implemented")
+
+	// This test ensures that we correctly serialize to JSON.
+	t.Run("MarshalJSON", func(t *testing.T) {
+		// testcase is a test case defined by this function
+		type testcase struct {
+			// name is the name of the test case
+			name string
+
+			// input is the input struct
+			input model.ArchivalNetworkEvent
+
+			// expectErr is the error we expect to see or nil
+			expectErr error
+
+			// expectData is the data we expect to see
+			expectData []byte
+		}
+
+		cases := []testcase{{
+			name: "serialization of a successful network event",
+			input: model.ArchivalNetworkEvent{
+				Address:       "8.8.8.8:443",
+				Failure:       nil,
+				NumBytes:      32768,
+				Operation:     "read",
+				Proto:         "tcp",
+				T0:            1.1,
+				T:             1.55,
+				TransactionID: 77,
+				Tags:          []string{"net"},
+			},
+			expectErr:  nil,
+			expectData: []byte(`{"address":"8.8.8.8:443","failure":null,"num_bytes":32768,"operation":"read","proto":"tcp","t0":1.1,"t":1.55,"transaction_id":77,"tags":["net"]}`),
+		}, {
+			name: "serialization of a failed network event",
+			input: model.ArchivalNetworkEvent{
+				Address: "8.8.8.8:443",
+				Failure: (func() *string {
+					s := netxlite.FailureGenericTimeoutError
+					return &s
+				})(),
+				NumBytes:      0,
+				Operation:     "read",
+				Proto:         "tcp",
+				T0:            1.1,
+				T:             7,
+				TransactionID: 144,
+				Tags:          []string{"net"},
+			},
+			expectErr:  nil,
+			expectData: []byte(`{"address":"8.8.8.8:443","failure":"generic_timeout_error","operation":"read","proto":"tcp","t0":1.1,"t":7,"transaction_id":144,"tags":["net"]}`),
+		}}
+
+		for _, tc := range cases {
+			t.Run(tc.name, func(t *testing.T) {
+				// serialize to JSON
+				data, err := json.Marshal(tc.input)
+
+				t.Log("got this error", err)
+				t.Log("got this raw data", data)
+				t.Logf("converted to string: %s", string(data))
+
+				// handle errors
+				switch {
+				case err == nil && tc.expectErr != nil:
+					t.Fatal("expected", tc.expectErr, "got", err)
+
+				case err != nil && tc.expectErr == nil:
+					t.Fatal("expected", tc.expectErr, "got", err)
+
+				case err != nil && tc.expectErr != nil:
+					if err.Error() != tc.expectErr.Error() {
+						t.Fatal("expected", tc.expectErr, "got", err)
+					}
+
+				case err == nil && tc.expectErr == nil:
+					// all good--fallthrough
+				}
+
+				// make sure the serialization is OK
+				if diff := cmp.Diff(tc.expectData, data); diff != "" {
+					t.Fatal(diff)
+				}
+			})
+		}
+	})
+
+	// This test ensures that we can unmarshal from the JSON representation
+	t.Run("UnmarshalJSON", func(t *testing.T) {
+		// testcase is a test case defined by this function
+		type testcase struct {
+			// name is the name of the test case
+			name string
+
+			// input is the binary input
+			input []byte
+
+			// expectErr is the error we expect to see or nil
+			expectErr error
+
+			// expectStruct is the struct we expect to see
+			expectStruct model.ArchivalNetworkEvent
+		}
+
+		cases := []testcase{{
+			name:      "deserialization of a successful network event",
+			expectErr: nil,
+			input:     []byte(`{"address":"8.8.8.8:443","failure":null,"num_bytes":32768,"operation":"read","proto":"tcp","t0":1.1,"t":1.55,"transaction_id":77,"tags":["net"]}`),
+			expectStruct: model.ArchivalNetworkEvent{
+				Address:       "8.8.8.8:443",
+				Failure:       nil,
+				NumBytes:      32768,
+				Operation:     "read",
+				Proto:         "tcp",
+				T0:            1.1,
+				T:             1.55,
+				TransactionID: 77,
+				Tags:          []string{"net"},
+			},
+		}, {
+			name:      "deserialization of a failed network event",
+			input:     []byte(`{"address":"8.8.8.8:443","failure":"generic_timeout_error","operation":"read","proto":"tcp","t0":1.1,"t":7,"transaction_id":144,"tags":["net"]}`),
+			expectErr: nil,
+			expectStruct: model.ArchivalNetworkEvent{
+				Address: "8.8.8.8:443",
+				Failure: (func() *string {
+					s := netxlite.FailureGenericTimeoutError
+					return &s
+				})(),
+				NumBytes:      0,
+				Operation:     "read",
+				Proto:         "tcp",
+				T0:            1.1,
+				T:             7,
+				TransactionID: 144,
+				Tags:          []string{"net"},
+			},
+		}}
+
+		for _, tc := range cases {
+			t.Run(tc.name, func(t *testing.T) {
+				// parse the JSON
+				var data model.ArchivalNetworkEvent
+				err := json.Unmarshal(tc.input, &data)
+
+				t.Log("got this error", err)
+				t.Logf("got this struct %+v", data)
+
+				// handle errors
+				switch {
+				case err == nil && tc.expectErr != nil:
+					t.Fatal("expected", tc.expectErr, "got", err)
+
+				case err != nil && tc.expectErr == nil:
+					t.Fatal("expected", tc.expectErr, "got", err)
+
+				case err != nil && tc.expectErr != nil:
+					if err.Error() != tc.expectErr.Error() {
+						t.Fatal("expected", tc.expectErr, "got", err)
+					}
+
+				case err == nil && tc.expectErr == nil:
+					// all good--fallthrough
+				}
+
+				// make sure the deserialization is OK
+				if diff := cmp.Diff(tc.expectStruct, data); diff != "" {
+					t.Fatal(diff)
+				}
+			})
+		}
+	})
 }