chore(test): More tests for HttpHeadersBuilder.

src/main/java/io/github/nstdio/http/ext/HttpHeadersBuilder.java

@@ -20,8 +20,10 @@
 import java.util.List;
 import java.util.Map;
 import java.util.TreeMap;
+import java.util.function.BiPredicate;
 
 class HttpHeadersBuilder {
+  private static final BiPredicate<String, String> ALWAYS_ALLOW = (s, s2) -> true;
   private final TreeMap<String, List<String>> headersMap;
 
   HttpHeadersBuilder() {
@@ -71,7 +73,7 @@ HttpHeadersBuilder set(String name, List<String> value) {
 
   HttpHeadersBuilder remove(String name, String value) {
     List<String> values = headersMap.get(name);
-    if (value != null) {
+    if (values != null) {
       values.remove(value);
       if (values.isEmpty()) {
         headersMap.remove(name);
@@ -86,7 +88,11 @@ HttpHeadersBuilder remove(String name) {
   }
 
   HttpHeaders build() {
-    return HttpHeaders.of(headersMap, (s, s2) -> true);
+    return build(ALWAYS_ALLOW);
+  }
+
+  HttpHeaders build(BiPredicate<String, String> filter) {
+    return HttpHeaders.of(headersMap, filter);
   }
 
   @Override

src/test/kotlin/io/github/nstdio/http/ext/Assertions.kt

@@ -96,6 +96,11 @@ object Assertions {
             return this
         }
 
+        fun isEmpty(): HttpHeadersAssertion {
+            assertThat(actual!!.map()).isEmpty()
+            return this
+        }
+
         fun hasHeaderWithOnlyValue(header: String?, value: String?): HttpHeadersAssertion {
             assertThat(actual!!.allValues(header))
                 .containsExactly(value)

src/test/kotlin/io/github/nstdio/http/ext/HttpHeadersBuilderTest.kt

@@ -0,0 +1,87 @@
+/*
+ * Copyright (C) 2022 Edgar Asatryan
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.github.nstdio.http.ext
+
+import io.github.nstdio.http.ext.Assertions.assertThat
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+
+internal class HttpHeadersBuilderTest {
+    private lateinit var builder: HttpHeadersBuilder
+
+    @BeforeEach
+    fun setUp() {
+        builder = HttpHeadersBuilder()
+    }
+
+    @Test
+    fun shouldSetHeader() {
+        //when
+        builder.add("abc", "1")
+        builder.set("abc", "2")
+
+        //then
+        assertThat(builder.build())
+            .hasHeaderWithOnlyValue("abc", "2")
+    }
+
+    @Test
+    fun `Should remove header single value`() {
+        //when
+        builder.add("abc", "1")
+        builder.add("abc", "2")
+        builder.remove("abc", "1")
+
+        //then
+        assertThat(builder.build())
+            .hasHeaderWithOnlyValue("abc", "2")
+    }
+
+    @Test
+    fun `Should safely remove not existing header`() {
+        //when
+        builder.remove("abc", "1")
+
+        //then
+        assertThat(builder.build())
+            .isEmpty()
+    }
+
+    @Test
+    fun `Should remove all entry if all removed single`() {
+        //when
+        builder.add("abc", "1")
+        builder.remove("abc", "1")
+
+        //then
+        assertThat(builder.build())
+            .isEmpty()
+    }
+
+    @Test
+    fun `Should remove all entry if all removed`() {
+        //when
+        builder.add("abc", "1")
+        builder.add("abc", "2")
+        builder.add("abcd", "2")
+        builder.remove("abc")
+
+        //then
+        assertThat(builder.build())
+            .hasNoHeader("abc")
+            .hasHeaderWithOnlyValue("abcd", "2")
+    }
+}