[propagator] Add injection integration test.

propagators/jaeger/jaeger_data_test.go

@@ -192,4 +192,78 @@ var invalidExtractHeaders = []extractTest{
 			jaegerHeader + "not": fmt.Sprintf("%s:%s:0:1", traceID32Str, spanIDStr),
 		},
 	},
+	{
+		name: "empty header value",
+		headers: map[string]string{
+			jaegerHeader: "",
+		},
+	},
+}
+
+type injectTest struct {
+	name        string
+	sc          trace.SpanContext
+	wantHeaders map[string]string
+}
+
+var injectHeaders = []injectTest{
+	{
+		name: "sampled",
+		sc: trace.SpanContext{
+			TraceID:    traceID,
+			SpanID:     spanID,
+			TraceFlags: trace.FlagsSampled,
+		},
+		wantHeaders: map[string]string{
+			jaegerHeader: fmt.Sprintf("%s:%s:0:1", traceID32Str, spanIDStr),
+		},
+	},
+	{
+		name: "debug",
+		sc: trace.SpanContext{
+			TraceID:    traceID,
+			SpanID:     spanID,
+			TraceFlags: trace.FlagsSampled | trace.FlagsDebug,
+		},
+		wantHeaders: map[string]string{
+			jaegerHeader: fmt.Sprintf("%s:%s:0:3", traceID32Str, spanIDStr),
+		},
+	},
+	{
+		name: "not sampled",
+		sc: trace.SpanContext{
+			TraceID: traceID,
+			SpanID:  spanID,
+		},
+		wantHeaders: map[string]string{
+			jaegerHeader: fmt.Sprintf("%s:%s:0:0", traceID32Str, spanIDStr),
+		},
+	},
+}
+
+var invalidInjectHeaders = []injectTest{
+	{
+		name: "empty",
+		sc:   trace.SpanContext{},
+	},
+	{
+		name: "missing traceID",
+		sc: trace.SpanContext{
+			SpanID:     spanID,
+			TraceFlags: trace.FlagsSampled,
+		},
+	},
+	{
+		name: "missing spanID",
+		sc: trace.SpanContext{
+			TraceID:    traceID,
+			TraceFlags: trace.FlagsSampled,
+		},
+	},
+	{
+		name: "missing both traceID and spanID",
+		sc: trace.SpanContext{
+			TraceFlags: trace.FlagsSampled,
+		},
+	},
 }

propagators/jaeger/jaeger_integration_test.go

@@ -21,11 +21,17 @@ import (
 
 	"github.com/google/go-cmp/cmp"
 
+	mocktracer "go.opentelemetry.io/contrib/internal/trace"
 	"go.opentelemetry.io/contrib/propagators/jaeger"
 	"go.opentelemetry.io/otel/api/propagation"
 	"go.opentelemetry.io/otel/api/trace"
 )
 
+var (
+	mockTracer  = mocktracer.NewTracer("")
+	_, mockSpan = mockTracer.Start(context.Background(), "")
+)
+
 func TestExtractJaeger(t *testing.T) {
 	testGroup := []struct {
 		name      string
@@ -62,3 +68,52 @@ func TestExtractJaeger(t *testing.T) {
 		}
 	}
 }
+
+type testSpan struct {
+	trace.Span
+	sc trace.SpanContext
+}
+
+func (s testSpan) SpanContext() trace.SpanContext {
+	return s.sc
+}
+
+func TestInjectJaeger(t *testing.T) {
+	testGroup := []struct {
+		name      string
+		testcases []injectTest
+	}{
+		{
+			name:      "valid test case",
+			testcases: injectHeaders,
+		},
+		{
+			name:      "invalid test case",
+			testcases: invalidInjectHeaders,
+		},
+	}
+
+	for _, tg := range testGroup {
+		for _, tc := range tg.testcases {
+			propagator := jaeger.Jaeger{}
+			t.Run(tc.name, func(t *testing.T) {
+				req, _ := http.NewRequest("GET", "http://example.com", nil)
+				ctx := trace.ContextWithSpan(
+					context.Background(),
+					testSpan{
+						Span: mockSpan,
+						sc:   tc.sc,
+					},
+				)
+				propagator.Inject(ctx, req.Header)
+
+				for h, v := range tc.wantHeaders {
+					result, want := req.Header.Get(h), v
+					if diff := cmp.Diff(result, want); diff != "" {
+						t.Errorf("%s: %s, header=%s: -got +want %s", tg.name, tc.name, h, diff)
+					}
+				}
+			})
+		}
+	}
+}

propagators/jaeger/jaeger_propagator.go

@@ -73,7 +73,9 @@ func (jaeger Jaeger) Inject(ctx context.Context, supplier propagation.HTTPSuppli
 		headers = append(headers, fmt.Sprintf("%x", flagsNotSampled))
 	}
 
-	supplier.Set(jaegerHeader, strings.Join(headers, separator))
+	if len(headers) == 4 {
+		supplier.Set(jaegerHeader, strings.Join(headers, separator))
+	}
 }
 
 func (jaeger Jaeger) Extract(ctx context.Context, supplier propagation.HTTPSupplier) context.Context {
@@ -89,10 +91,6 @@ func (jaeger Jaeger) Extract(ctx context.Context, supplier propagation.HTTPSuppl
 }
 
 func extract(headerVal string) (trace.SpanContext, error) {
-	if headerVal == "" {
-		return empty, errEmptyContext
-	}
-
 	var (
 		sc  = trace.SpanContext{}
 		err error