diff --git a/pom.xml b/pom.xml
index adf3f5cda..d5de2d04f 100644
--- a/pom.xml
+++ b/pom.xml
@@ -61,6 +61,11 @@
       <artifactId>lombok</artifactId>
       <optional>true</optional>
     </dependency>
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-starter-test</artifactId>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 
   <build>
diff --git a/src/test/java/com/openisle/controller/AdminControllerTest.java b/src/test/java/com/openisle/controller/AdminControllerTest.java
new file mode 100644
index 000000000..e50c82cb3
--- /dev/null
+++ b/src/test/java/com/openisle/controller/AdminControllerTest.java
@@ -0,0 +1,25 @@
+package com.openisle.controller;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
+import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
+import org.springframework.test.web.servlet.MockMvc;
+
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.jsonPath;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
+
+@WebMvcTest(AdminController.class)
+@AutoConfigureMockMvc(addFilters = false)
+class AdminControllerTest {
+    @Autowired
+    private MockMvc mockMvc;
+
+    @Test
+    void adminHelloReturnsMessage() throws Exception {
+        mockMvc.perform(get("/api/admin/hello"))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.message").value("Hello, Admin User"));
+    }
+}
diff --git a/src/test/java/com/openisle/controller/AuthControllerTest.java b/src/test/java/com/openisle/controller/AuthControllerTest.java
new file mode 100644
index 000000000..cdc73798d
--- /dev/null
+++ b/src/test/java/com/openisle/controller/AuthControllerTest.java
@@ -0,0 +1,90 @@
+package com.openisle.controller;
+
+import com.openisle.model.User;
+import com.openisle.service.EmailService;
+import com.openisle.service.JwtService;
+import com.openisle.service.UserService;
+import org.junit.jupiter.api.Test;
+import org.mockito.Mockito;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
+import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
+import org.springframework.boot.test.mock.mockito.MockBean;
+import org.springframework.http.MediaType;
+import org.springframework.test.web.servlet.MockMvc;
+
+import java.util.Map;
+import java.util.Optional;
+
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.post;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.jsonPath;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
+
+@WebMvcTest(AuthController.class)
+@AutoConfigureMockMvc(addFilters = false)
+class AuthControllerTest {
+    @Autowired
+    private MockMvc mockMvc;
+
+    @MockBean
+    private UserService userService;
+    @MockBean
+    private JwtService jwtService;
+    @MockBean
+    private EmailService emailService;
+
+    @Test
+    void registerSendsEmail() throws Exception {
+        User user = new User();
+        user.setEmail("a@b.com");
+        user.setUsername("u");
+        user.setVerificationCode("123456");
+        Mockito.when(userService.register(eq("u"), eq("a@b.com"), eq("p"))).thenReturn(user);
+
+        mockMvc.perform(post("/api/auth/register")
+                        .contentType(MediaType.APPLICATION_JSON)
+                        .content("{\"username\":\"u\",\"email\":\"a@b.com\",\"password\":\"p\"}"))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.message").exists());
+
+        Mockito.verify(emailService).sendEmail(eq("a@b.com"), any(), any());
+    }
+
+    @Test
+    void verifyCodeEndpoint() throws Exception {
+        Mockito.when(userService.verifyCode("u", "123")).thenReturn(true);
+
+        mockMvc.perform(post("/api/auth/verify")
+                        .contentType(MediaType.APPLICATION_JSON)
+                        .content("{\"username\":\"u\",\"code\":\"123\"}"))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.message").value("Verified"));
+    }
+
+    @Test
+    void loginReturnsToken() throws Exception {
+        User user = new User();
+        user.setUsername("u");
+        Mockito.when(userService.authenticate("u", "p")).thenReturn(Optional.of(user));
+        Mockito.when(jwtService.generateToken("u")).thenReturn("token");
+
+        mockMvc.perform(post("/api/auth/login")
+                        .contentType(MediaType.APPLICATION_JSON)
+                        .content("{\"username\":\"u\",\"password\":\"p\"}"))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.token").value("token"));
+    }
+
+    @Test
+    void loginFails() throws Exception {
+        Mockito.when(userService.authenticate("u", "bad")).thenReturn(Optional.empty());
+
+        mockMvc.perform(post("/api/auth/login")
+                        .contentType(MediaType.APPLICATION_JSON)
+                        .content("{\"username\":\"u\",\"password\":\"bad\"}"))
+                .andExpect(status().isBadRequest())
+                .andExpect(jsonPath("$.error").value("Invalid credentials or user not verified"));
+    }
+}
diff --git a/src/test/java/com/openisle/controller/CommentControllerTest.java b/src/test/java/com/openisle/controller/CommentControllerTest.java
new file mode 100644
index 000000000..228b84543
--- /dev/null
+++ b/src/test/java/com/openisle/controller/CommentControllerTest.java
@@ -0,0 +1,77 @@
+package com.openisle.controller;
+
+import com.openisle.model.Comment;
+import com.openisle.model.Post;
+import com.openisle.model.User;
+import com.openisle.service.CommentService;
+import org.junit.jupiter.api.Test;
+import org.mockito.Mockito;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
+import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
+import org.springframework.boot.test.mock.mockito.MockBean;
+import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
+import org.springframework.test.web.servlet.MockMvc;
+
+import java.time.LocalDateTime;
+import java.util.List;
+
+import static org.mockito.ArgumentMatchers.eq;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.post;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.jsonPath;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
+
+@WebMvcTest(CommentController.class)
+@AutoConfigureMockMvc(addFilters = false)
+class CommentControllerTest {
+    @Autowired
+    private MockMvc mockMvc;
+
+    @MockBean
+    private CommentService commentService;
+
+    private Comment createComment(Long id, String content, String authorName) {
+        User user = new User();
+        user.setUsername(authorName);
+        Comment c = new Comment();
+        c.setId(id);
+        c.setContent(content);
+        c.setCreatedAt(LocalDateTime.now());
+        c.setAuthor(user);
+        c.setPost(new Post());
+        return c;
+    }
+
+    @Test
+    void createAndListComments() throws Exception {
+        Comment comment = createComment(1L, "hi", "bob");
+        Mockito.when(commentService.addComment(eq("bob"), eq(1L), eq("hi"))).thenReturn(comment);
+        Mockito.when(commentService.getCommentsForPost(1L)).thenReturn(List.of(comment));
+        Mockito.when(commentService.getReplies(1L)).thenReturn(List.of());
+
+        mockMvc.perform(post("/api/posts/1/comments")
+                        .contentType("application/json")
+                        .content("{\"content\":\"hi\"}")
+                        .principal(new UsernamePasswordAuthenticationToken("bob", "p")))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.content").value("hi"));
+
+        mockMvc.perform(get("/api/posts/1/comments"))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$[0].id").value(1));
+    }
+
+    @Test
+    void replyComment() throws Exception {
+        Comment reply = createComment(2L, "re", "alice");
+        Mockito.when(commentService.addReply(eq("alice"), eq(1L), eq("re"))).thenReturn(reply);
+
+        mockMvc.perform(post("/api/comments/1/replies")
+                        .contentType("application/json")
+                        .content("{\"content\":\"re\"}")
+                        .principal(new UsernamePasswordAuthenticationToken("alice", "p")))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.id").value(2));
+    }
+}
diff --git a/src/test/java/com/openisle/controller/HelloControllerTest.java b/src/test/java/com/openisle/controller/HelloControllerTest.java
new file mode 100644
index 000000000..9a9769b91
--- /dev/null
+++ b/src/test/java/com/openisle/controller/HelloControllerTest.java
@@ -0,0 +1,25 @@
+package com.openisle.controller;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
+import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
+import org.springframework.test.web.servlet.MockMvc;
+
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.jsonPath;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
+
+@WebMvcTest(HelloController.class)
+@AutoConfigureMockMvc(addFilters = false)
+class HelloControllerTest {
+    @Autowired
+    private MockMvc mockMvc;
+
+    @Test
+    void helloReturnsMessage() throws Exception {
+        mockMvc.perform(get("/api/hello"))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.message").value("Hello, Authenticated User"));
+    }
+}
diff --git a/src/test/java/com/openisle/controller/PostControllerTest.java b/src/test/java/com/openisle/controller/PostControllerTest.java
new file mode 100644
index 000000000..9f027216e
--- /dev/null
+++ b/src/test/java/com/openisle/controller/PostControllerTest.java
@@ -0,0 +1,75 @@
+package com.openisle.controller;
+
+import com.openisle.model.Post;
+import com.openisle.model.User;
+import com.openisle.service.PostService;
+import org.junit.jupiter.api.Test;
+import org.mockito.Mockito;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
+import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
+import org.springframework.boot.test.mock.mockito.MockBean;
+import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
+import org.springframework.test.web.servlet.MockMvc;
+
+import java.time.LocalDateTime;
+import java.util.List;
+
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.post;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.jsonPath;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
+
+@WebMvcTest(PostController.class)
+@AutoConfigureMockMvc(addFilters = false)
+class PostControllerTest {
+    @Autowired
+    private MockMvc mockMvc;
+
+    @MockBean
+    private PostService postService;
+
+    @Test
+    void createAndGetPost() throws Exception {
+        User user = new User();
+        user.setUsername("alice");
+        Post post = new Post();
+        post.setId(1L);
+        post.setTitle("t");
+        post.setContent("c");
+        post.setCreatedAt(LocalDateTime.now());
+        post.setAuthor(user);
+        Mockito.when(postService.createPost(eq("alice"), eq("t"), eq("c"))).thenReturn(post);
+        Mockito.when(postService.getPost(1L)).thenReturn(post);
+
+        mockMvc.perform(post("/api/posts")
+                        .contentType("application/json")
+                        .content("{\"title\":\"t\",\"content\":\"c\"}")
+                        .principal(new UsernamePasswordAuthenticationToken("alice", "p")))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.title").value("t"));
+
+        mockMvc.perform(get("/api/posts/1"))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.id").value(1));
+    }
+
+    @Test
+    void listPosts() throws Exception {
+        User user = new User();
+        user.setUsername("bob");
+        Post post = new Post();
+        post.setId(2L);
+        post.setTitle("hello");
+        post.setContent("world");
+        post.setCreatedAt(LocalDateTime.now());
+        post.setAuthor(user);
+        Mockito.when(postService.listPosts()).thenReturn(List.of(post));
+
+        mockMvc.perform(get("/api/posts"))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$[0].title").value("hello"));
+    }
+}
diff --git a/src/test/java/com/openisle/controller/ReactionControllerTest.java b/src/test/java/com/openisle/controller/ReactionControllerTest.java
new file mode 100644
index 000000000..8faaef469
--- /dev/null
+++ b/src/test/java/com/openisle/controller/ReactionControllerTest.java
@@ -0,0 +1,73 @@
+package com.openisle.controller;
+
+import com.openisle.model.Comment;
+import com.openisle.model.Post;
+import com.openisle.model.Reaction;
+import com.openisle.model.ReactionType;
+import com.openisle.model.User;
+import com.openisle.service.ReactionService;
+import org.junit.jupiter.api.Test;
+import org.mockito.Mockito;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
+import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
+import org.springframework.boot.test.mock.mockito.MockBean;
+import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
+import org.springframework.test.web.servlet.MockMvc;
+
+import static org.mockito.ArgumentMatchers.eq;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.post;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.jsonPath;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
+
+@WebMvcTest(ReactionController.class)
+@AutoConfigureMockMvc(addFilters = false)
+class ReactionControllerTest {
+    @Autowired
+    private MockMvc mockMvc;
+
+    @MockBean
+    private ReactionService reactionService;
+
+    @Test
+    void reactToPost() throws Exception {
+        User user = new User();
+        user.setUsername("u1");
+        Post post = new Post();
+        post.setId(1L);
+        Reaction reaction = new Reaction();
+        reaction.setId(1L);
+        reaction.setUser(user);
+        reaction.setPost(post);
+        reaction.setType(ReactionType.LIKE);
+        Mockito.when(reactionService.reactToPost(eq("u1"), eq(1L), eq(ReactionType.LIKE))).thenReturn(reaction);
+
+        mockMvc.perform(post("/api/posts/1/reactions")
+                        .contentType("application/json")
+                        .content("{\"type\":\"LIKE\"}")
+                        .principal(new UsernamePasswordAuthenticationToken("u1", "p")))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.postId").value(1));
+    }
+
+    @Test
+    void reactToComment() throws Exception {
+        User user = new User();
+        user.setUsername("u2");
+        Comment comment = new Comment();
+        comment.setId(2L);
+        Reaction reaction = new Reaction();
+        reaction.setId(2L);
+        reaction.setUser(user);
+        reaction.setComment(comment);
+        reaction.setType(ReactionType.RECOMMEND);
+        Mockito.when(reactionService.reactToComment(eq("u2"), eq(2L), eq(ReactionType.RECOMMEND))).thenReturn(reaction);
+
+        mockMvc.perform(post("/api/comments/2/reactions")
+                        .contentType("application/json")
+                        .content("{\"type\":\"RECOMMEND\"}")
+                        .principal(new UsernamePasswordAuthenticationToken("u2", "p")))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.commentId").value(2));
+    }
+}