diff --git a/.vscode/settings.json b/.vscode/settings.json
index 29dd869..afac938 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -1,6 +1,5 @@
 {
   "editor.formatOnSave": true,
-  "editor.codeActionsOnSaveTimeout": 2000,
   "editor.codeActionsOnSave": {
     "source.fixAll.eslint": true
   },
diff --git a/README.md b/README.md
index dfdb784..e222d28 100644
--- a/README.md
+++ b/README.md
@@ -29,6 +29,14 @@ The following inputs are supported.
 
 - `channel` - (required) The channel to be notified of results.
 
+- `text` - (optional) Overrides main body text of the message.
+
+- `username` - (optional) Overrides bot's user name.
+
+- `icon_emoji` - (optional) Emoji to use as the icon for this message. Overrides `icon_url`.
+
+- `icon_url` - (optional) URL to an image to use as the icon for this message.
+
 For more information, see https://api.slack.com/methods/chat.postMessage.
 
 ## Output
diff --git a/action.yaml b/action.yaml
index d4f4da1..7f6130c 100644
--- a/action.yaml
+++ b/action.yaml
@@ -19,19 +19,19 @@ inputs:
     description: The channel to be notified of results.
     required: true
   text:
-    description: todo
+    description: Override main body text of the message.
     required: false
     default: ''
   username:
-    description: todo
+    description: Override bot's user name.
     required: false
     default: ''
   icon_emoji:
-    description: todo
+    description: Emoji to use as the icon for this message. Overrides `icon_url`.
     required: false
     default: ''
   icon_url:
-    description: todo
+    description: URL to an image to use as the icon for this message.
     required: false
     default: ''
 
diff --git a/dist/index.js b/dist/index.js
index c502972..394a08f 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -4643,80 +4643,6 @@ class PQueue {
 module.exports = PQueue;
 
 
-/***/ }),
-
-/***/ 184:
-/***/ (function(__unusedmodule, exports, __webpack_require__) {
-
-"use strict";
-
-var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
-    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
-    return new (P || (P = Promise))(function (resolve, reject) {
-        function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
-        function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
-        step((generator = generator.apply(thisArg, _arguments || [])).next());
-    });
-};
-Object.defineProperty(exports, "__esModule", { value: true });
-const github_1 = __webpack_require__(469);
-const status_1 = __webpack_require__(895);
-const default_1 = __webpack_require__(594);
-const quote = (value) => '```' + value + '```';
-exports.messageFactory = ({ status: rawStatus, githubToken, channel }) => __awaiter(void 0, void 0, void 0, function* () {
-    const octokit = new github_1.GitHub(githubToken);
-    const { sha, workflow } = github_1.context;
-    const { owner, repo } = github_1.context.repo;
-    const { data } = yield octokit.repos.getCommit({ owner, repo, ref: sha });
-    const commitMessage = data.commit.message;
-    const githubRepo = `${owner}/${repo}`;
-    const githubRepoURL = `https://github.com/${owner}/${repo}`;
-    const status = status_1.getStatus(rawStatus);
-    /* eslint-disable @typescript-eslint/camelcase */
-    const attachment = {
-        color: default_1.defaultColors[status.type],
-        fields: [
-            {
-                title: 'Commit Message',
-                value: quote(commitMessage),
-                short: false
-            },
-            {
-                title: 'Repository',
-                value: `<${githubRepoURL}/tree/${sha}|${githubRepo}>`,
-                short: true
-            },
-            {
-                title: 'Workflow',
-                value: `<https://github.com/${owner}/${repo}/commit/${sha}/checks|${workflow}>`,
-                short: true
-            },
-            {
-                title: 'Status',
-                value: status.value,
-                short: true
-            },
-            {
-                title: 'Commit',
-                value: `<${githubRepoURL}/commit/${sha}|${sha.substring(0, 7)}>`,
-                short: true
-            }
-        ],
-        footer_icon: default_1.defaultFooterIcon,
-        footer: default_1.defaultFooter,
-        ts: `${Math.floor(Date.now() / 1000)}`,
-        mrkdwn_in: ['fields', 'text']
-    };
-    return {
-        channel: channel,
-        text: default_1.defaultText[status.type],
-        attachments: [attachment]
-    };
-    /* eslint-enable @typescript-eslint/camelcase */
-});
-
-
 /***/ }),
 
 /***/ 190:
@@ -4881,17 +4807,24 @@ var __importStar = (this && this.__importStar) || function (mod) {
 Object.defineProperty(exports, "__esModule", { value: true });
 const core = __importStar(__webpack_require__(470));
 const web_api_1 = __webpack_require__(114);
-const factory_1 = __webpack_require__(184);
+const builder_1 = __webpack_require__(532);
 function run() {
     return __awaiter(this, void 0, void 0, function* () {
         try {
-            const token = core.getInput('oauth_token');
+            const token = core.getInput('oauth_token', { required: true });
             const client = new web_api_1.WebClient(token);
             core.info('[Info] Slack client has been initialized.');
-            const status = core.getInput('status');
-            const githubToken = core.getInput('github_token');
-            const channel = core.getInput('channel');
-            const message = yield factory_1.messageFactory({ status, githubToken, channel });
+            const optional = (value) => (value === '' ? undefined : value);
+            const builder = new builder_1.MessageBuilder({
+                status: core.getInput('status', { required: true }),
+                githubToken: core.getInput('github_token', { required: true }),
+                channel: core.getInput('channel', { required: true }),
+                text: optional(core.getInput('text')),
+                username: optional(core.getInput('username')),
+                iconEmoji: optional(core.getInput('icon_emoji')),
+                iconURL: optional(core.getInput('icon_url'))
+            });
+            const message = yield builder.build();
             const { ok, error } = yield client.chat.postMessage(message);
             core.info(`[Info] Request result is ${ok}`);
             if (error) {
@@ -23578,6 +23511,108 @@ utils.forEach(['post', 'put', 'patch'], function forEachMethodWithData(method) {
 module.exports = defaults;
 
 
+/***/ }),
+
+/***/ 532:
+/***/ (function(__unusedmodule, exports, __webpack_require__) {
+
+"use strict";
+
+var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
+    return new (P || (P = Promise))(function (resolve, reject) {
+        function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
+        function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
+        step((generator = generator.apply(thisArg, _arguments || [])).next());
+    });
+};
+Object.defineProperty(exports, "__esModule", { value: true });
+const github_1 = __webpack_require__(469);
+const status_1 = __webpack_require__(895);
+const default_1 = __webpack_require__(594);
+class MessageBuilder {
+    constructor(option, mock) {
+        var _a;
+        this.option = option;
+        this.context = (_a = mock === null || mock === void 0 ? void 0 : mock.context) !== null && _a !== void 0 ? _a : github_1.context; // Use mock
+        this.mockCommitMessage = mock === null || mock === void 0 ? void 0 : mock.commitMessage;
+    }
+    quote(value) {
+        return '```' + value + '```';
+    }
+    fetchCommitMessage() {
+        return __awaiter(this, void 0, void 0, function* () {
+            const { option, context, mockCommitMessage } = this;
+            if (mockCommitMessage)
+                return mockCommitMessage; // Use mock
+            const { sha } = context;
+            const { owner, repo } = context.repo;
+            const octokit = new github_1.GitHub(option.githubToken);
+            const { data } = yield octokit.repos.getCommit({ owner, repo, ref: sha });
+            return data.commit.message;
+        });
+    }
+    build() {
+        var _a;
+        return __awaiter(this, void 0, void 0, function* () {
+            const { option } = this;
+            const { sha, workflow } = github_1.context;
+            const { owner, repo } = github_1.context.repo;
+            const githubRepo = `${owner}/${repo}`;
+            const githubRepoURL = `https://github.com/${owner}/${repo}`;
+            const status = status_1.getStatus(option.status);
+            // Build attachment fields
+            const fields = [];
+            const commitMessage = yield this.fetchCommitMessage();
+            fields.push({
+                title: 'Commit Message',
+                value: this.quote(commitMessage),
+                short: false
+            });
+            fields.push({
+                title: 'Repository',
+                value: `<${githubRepoURL}/tree/${sha}|${githubRepo}>`,
+                short: true
+            });
+            fields.push({
+                title: 'Workflow',
+                value: `<${githubRepoURL}/commit/${sha}/checks|${workflow}>`,
+                short: true
+            });
+            fields.push({
+                title: 'Status',
+                value: status.value,
+                short: true
+            });
+            fields.push({
+                title: 'Commit',
+                value: `<${githubRepoURL}/commit/${sha}|${sha.substring(0, 7)}>`,
+                short: true
+            });
+            /* eslint-disable @typescript-eslint/camelcase */
+            const attachment = {
+                color: default_1.defaultColors[status.type],
+                fields: fields,
+                footer_icon: default_1.defaultFooterIcon,
+                footer: default_1.defaultFooter,
+                ts: `${Math.floor(Date.now() / 1000)}`,
+                mrkdwn_in: ['fields', 'text']
+            };
+            return {
+                channel: option.channel,
+                text: (_a = option.text) !== null && _a !== void 0 ? _a : default_1.defaultText[status.type],
+                attachments: [attachment],
+                username: option.username,
+                icon_emoji: option.iconEmoji,
+                icon_url: option.iconURL
+            };
+        });
+    }
+}
+exports.MessageBuilder = MessageBuilder;
+
+
 /***/ }),
 
 /***/ 536:
diff --git a/src/builder.ts b/src/builder.ts
new file mode 100644
index 0000000..73b76a8
--- /dev/null
+++ b/src/builder.ts
@@ -0,0 +1,108 @@
+import { ChatPostMessageArguments, MessageAttachment } from '@slack/web-api'
+import { GitHub, context } from '@actions/github'
+import { Context } from '@actions/github/lib/context'
+import { getStatus } from './status'
+import { defaultColors, defaultText, defaultFooter, defaultFooterIcon } from './default'
+
+type Builder<T> = {
+  build: () => Promise<T>
+}
+
+export type MessageBuilderOption = {
+  status: string
+  channel: string
+  text?: string
+  username?: string
+  iconEmoji?: string
+  iconURL?: string
+  githubToken: string
+}
+
+export type MessageBuilderMockOption = {
+  context: Context
+  commitMessage: string
+}
+
+export class MessageBuilder implements Builder<ChatPostMessageArguments> {
+  private context: Context
+  private mockCommitMessage?: string
+  constructor(private option: MessageBuilderOption, mock?: MessageBuilderMockOption) {
+    this.context = mock?.context ?? context // Use mock
+    this.mockCommitMessage = mock?.commitMessage
+  }
+
+  private quote(value: string) {
+    return '```' + value + '```'
+  }
+
+  private async fetchCommitMessage(): Promise<string> {
+    const { option, context, mockCommitMessage } = this
+    if (mockCommitMessage) return mockCommitMessage // Use mock
+
+    const { sha } = context
+    const { owner, repo } = context.repo
+    const octokit = new GitHub(option.githubToken)
+    const { data } = await octokit.repos.getCommit({ owner, repo, ref: sha })
+    return data.commit.message
+  }
+
+  async build(): Promise<ChatPostMessageArguments> {
+    const { option } = this
+    const { sha, workflow } = context
+    const { owner, repo } = context.repo
+
+    const githubRepo = `${owner}/${repo}`
+    const githubRepoURL = `https://github.com/${owner}/${repo}`
+
+    const status = getStatus(option.status)
+
+    // Build attachment fields
+    const fields: NonNullable<MessageAttachment['fields']> = []
+    const commitMessage = await this.fetchCommitMessage()
+    fields.push({
+      title: 'Commit Message',
+      value: this.quote(commitMessage),
+      short: false
+    })
+    fields.push({
+      title: 'Repository',
+      value: `<${githubRepoURL}/tree/${sha}|${githubRepo}>`,
+      short: true
+    })
+    fields.push({
+      title: 'Workflow',
+      value: `<${githubRepoURL}/commit/${sha}/checks|${workflow}>`,
+      short: true
+    })
+    fields.push({
+      title: 'Status',
+      value: status.value,
+      short: true
+    })
+    fields.push({
+      title: 'Commit',
+      value: `<${githubRepoURL}/commit/${sha}|${sha.substring(0, 7)}>`,
+      short: true
+    })
+
+    /* eslint-disable @typescript-eslint/camelcase */
+    const attachment: MessageAttachment = {
+      color: defaultColors[status.type],
+      fields: fields,
+      footer_icon: defaultFooterIcon,
+      footer: defaultFooter,
+      ts: `${Math.floor(Date.now() / 1000)}`,
+      mrkdwn_in: ['fields', 'text']
+    }
+
+    return {
+      channel: option.channel,
+      text: option.text ?? defaultText[status.type],
+      attachments: [attachment],
+      username: option.username,
+      icon_emoji: option.iconEmoji,
+      icon_url: option.iconURL
+    }
+    /* eslint-enable @typescript-eslint/camelcase */
+  }
+}
diff --git a/src/factory.ts b/src/factory.ts
deleted file mode 100644
index 3999f76..0000000
--- a/src/factory.ts
+++ /dev/null
@@ -1,70 +0,0 @@
-import { ChatPostMessageArguments, MessageAttachment } from '@slack/web-api'
-import { GitHub, context } from '@actions/github'
-import { getStatus } from './status'
-import { defaultColors, defaultText, defaultFooter, defaultFooterIcon } from './default'
-
-const quote = (value: string) => '```' + value + '```'
-
-export type MessageFactoryArguments = {
-  status: string
-  githubToken: string
-  channel: string
-}
-
-type MessageFactory = (args: MessageFactoryArguments) => Promise<ChatPostMessageArguments>
-
-export const messageFactory: MessageFactory = async ({ status: rawStatus, githubToken, channel }) => {
-  const octokit = new GitHub(githubToken)
-  const { sha, workflow } = context
-  const { owner, repo } = context.repo
-  const { data } = await octokit.repos.getCommit({ owner, repo, ref: sha })
-  const commitMessage = data.commit.message
-
-  const githubRepo = `${owner}/${repo}`
-  const githubRepoURL = `https://github.com/${owner}/${repo}`
-
-  const status = getStatus(rawStatus)
-
-  /* eslint-disable @typescript-eslint/camelcase */
-  const attachment: MessageAttachment = {
-    color: defaultColors[status.type],
-    fields: [
-      {
-        title: 'Commit Message',
-        value: quote(commitMessage),
-        short: false
-      },
-      {
-        title: 'Repository',
-        value: `<${githubRepoURL}/tree/${sha}|${githubRepo}>`,
-        short: true
-      },
-      {
-        title: 'Workflow',
-        value: `<https://github.com/${owner}/${repo}/commit/${sha}/checks|${workflow}>`,
-        short: true
-      },
-      {
-        title: 'Status',
-        value: status.value,
-        short: true
-      },
-      {
-        title: 'Commit',
-        value: `<${githubRepoURL}/commit/${sha}|${sha.substring(0, 7)}>`,
-        short: true
-      }
-    ],
-    footer_icon: defaultFooterIcon,
-    footer: defaultFooter,
-    ts: `${Math.floor(Date.now() / 1000)}`,
-    mrkdwn_in: ['fields', 'text']
-  }
-
-  return {
-    channel: channel,
-    text: defaultText[status.type],
-    attachments: [attachment]
-  }
-  /* eslint-enable @typescript-eslint/camelcase */
-}
diff --git a/src/main.ts b/src/main.ts
index 0bd3933..f67d178 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -1,18 +1,26 @@
 import * as core from '@actions/core'
 import { WebClient } from '@slack/web-api'
-import { messageFactory } from './factory'
+import { MessageBuilder } from './builder'
 
 async function run(): Promise<void> {
   try {
-    const token = core.getInput('oauth_token')
+    const token = core.getInput('oauth_token', { required: true })
     const client = new WebClient(token)
     core.info('[Info] Slack client has been initialized.')
 
-    const status = core.getInput('status')
-    const githubToken = core.getInput('github_token')
-    const channel = core.getInput('channel')
+    const optional = <T extends string>(value: T) => (value === '' ? undefined : value)
+
+    const builder = new MessageBuilder({
+      status: core.getInput('status', { required: true }),
+      githubToken: core.getInput('github_token', { required: true }),
+      channel: core.getInput('channel', { required: true }),
+      text: optional(core.getInput('text')),
+      username: optional(core.getInput('username')),
+      iconEmoji: optional(core.getInput('icon_emoji')),
+      iconURL: optional(core.getInput('icon_url'))
+    })
+    const message = await builder.build()
 
-    const message = await messageFactory({ status, githubToken, channel })
     const { ok, error } = await client.chat.postMessage(message)
     core.info(`[Info] Request result is ${ok}`)
     if (error) {