Update test and changelog

CHANGELOG.asciidoc

@@ -35,6 +35,7 @@ https://github.com/elastic/beats/compare/v6.0.0-beta2...master[Check the HEAD di
 - Fix data race accessing watched containers. {issue}5147[5147]
 - Remove ID() from Runner interface {issue}5153[5153]
 - Do not require template if index change and template disabled {pull}5319[5319]
+- Avoid double slash when join url and path {pull}5517[5517]
 
 *Auditbeat*
 

libbeat/outputs/elasticsearch/client_test.go

@@ -313,3 +313,49 @@ func TestClientWithHeaders(t *testing.T) {
 	assert.NoError(t, err)
 	assert.Equal(t, 2, requestCount)
 }
+
+func TestAddToURL(t *testing.T) {
+	type Test struct {
+		url      string
+		path     string
+		pipeline string
+		params   map[string]string
+		expected string
+	}
+	tests := []Test{
+		{
+			url:      "localhost:9200",
+			path:     "/path",
+			pipeline: "",
+			params:   make(map[string]string),
+			expected: "localhost:9200/path",
+		},
+		{
+			url:      "localhost:9200/",
+			path:     "/path",
+			pipeline: "",
+			params:   make(map[string]string),
+			expected: "localhost:9200/path",
+		},
+		{
+			url:      "localhost:9200",
+			path:     "/path",
+			pipeline: "pipeline_1",
+			params:   make(map[string]string),
+			expected: "localhost:9200/path?pipeline=pipeline_1",
+		},
+		{
+			url:      "localhost:9200/",
+			path:     "/path",
+			pipeline: "",
+			params: map[string]string{
+				"param": "value",
+			},
+			expected: "localhost:9200/path?param=value",
+		},
+	}
+	for _, test := range tests {
+		url := addToURL(test.url, test.path, test.pipeline, test.params)
+		assert.Equal(t, url, test.expected)
+	}
+}