test(component): React 컴포넌트 테스트 도입 (Testing Library, 13개)

단위(순수함수)와 E2E(전체 흐름) 사이 '부품 렌더링' 층을 메운다(jsdom).
- Badge(3): 코드값→한국어 라벨/색 매핑, 미지값 폴백(방어적 기본값)
- ProgressBar(4): 백분율 계산·반올림, 0 나눗셈 방어(NaN 방지), 막대 너비
- CodeEditor(6): 제어 입력 왕복, 줄번호 minRows 보장/증가, Tab 공백2칸 삽입,
  텍스트 선택 후 Tab 커서 위치(selectionStart+2 회귀 방지 — 과거 버그 못 박기)

세팅: @testing-library/react+jest-dom+user-event+jsdom, 파일별 @vitest-environment,
매 테스트 후 cleanup(globals 미사용 시 DOM 누적 방지).

프론트 테스트 9→22. coverage 게이트·lint·build 통과.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/package-lock.json

@@ -17,15 +17,48 @@
       "devDependencies": {
         "@eslint/js": "^9.17.0",
         "@playwright/test": "1.49.1",
+        "@testing-library/dom": "^10.4.0",
+        "@testing-library/jest-dom": "^6.6.3",
+        "@testing-library/react": "^16.1.0",
+        "@testing-library/user-event": "^14.5.2",
         "@vitejs/plugin-react": "^4.3.4",
         "@vitest/coverage-v8": "^4.1.10",
         "eslint": "^9.17.0",
         "eslint-plugin-react-hooks": "^5.1.0",
         "globals": "^15.14.0",
+        "jsdom": "^26.0.0",
         "vite": "^6.0.7",
         "vitest": "^4.1.10"
       }
     },
+    "node_modules/@adobe/css-tools": {
+      "version": "4.5.0",
+      "resolved": "https://registry.npmjs.org/@adobe/css-tools/-/css-tools-4.5.0.tgz",
+      "integrity": "sha512-6OzddxPio9UiWTCemp4N8cYLV2ZN1ncRnV1cVGtve7dhPOtRkleRyx32GQCYSwDYgaHU3USMm84tNsvKzRCa1Q==",
+      "dev": true,
+      "license": "MIT"
+    },
+    "node_modules/@asamuzakjp/css-color": {
+      "version": "3.2.0",
+      "resolved": "https://registry.npmjs.org/@asamuzakjp/css-color/-/css-color-3.2.0.tgz",
+      "integrity": "sha512-K1A6z8tS3XsmCMM86xoWdn7Fkdn9m6RSVtocUrJYIwZnFVkng/PvkEoWtOWmP+Scc6saYWHWZYbndEEXxl24jw==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@csstools/css-calc": "^2.1.3",
+        "@csstools/css-color-parser": "^3.0.9",
+        "@csstools/css-parser-algorithms": "^3.0.4",
+        "@csstools/css-tokenizer": "^3.0.3",
+        "lru-cache": "^10.4.3"
+      }
+    },
+    "node_modules/@asamuzakjp/css-color/node_modules/lru-cache": {
+      "version": "10.4.3",
+      "resolved": "https://registry.npmjs.org/lru-cache/-/lru-cache-10.4.3.tgz",
+      "integrity": "sha512-JNAzZcXrCt42VGLuYz0zfAzDfAvJWW6AfYlDBQyDV5DClI2m5sAmK+OIO7s59XfsRsWHp02jAJrRadPRGTt6SQ==",
+      "dev": true,
+      "license": "ISC"
+    },
     "node_modules/@babel/code-frame": {
       "version": "7.29.7",
       "resolved": "https://registry.npmjs.org/@babel/code-frame/-/code-frame-7.29.7.tgz",
@@ -260,6 +293,16 @@
         "@babel/core": "^7.0.0-0"
       }
     },
+    "node_modules/@babel/runtime": {
+      "version": "7.29.7",
+      "resolved": "https://registry.npmjs.org/@babel/runtime/-/runtime-7.29.7.tgz",
+      "integrity": "sha512-Nq8OhGWiZIZGV6hLHoyAKLLcJihP/xFeBMGJoUrxTX2psI8dCifzLhZISFb+VWS3wFMRDmCGw5R+dOySCqPLhw==",
+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": ">=6.9.0"
+      }
+    },
     "node_modules/@babel/template": {
       "version": "7.29.7",
       "resolved": "https://registry.npmjs.org/@babel/template/-/template-7.29.7.tgz",
@@ -318,6 +361,121 @@
         "node": ">=18"
       }
     },
+    "node_modules/@csstools/color-helpers": {
+      "version": "5.1.0",
+      "resolved": "https://registry.npmjs.org/@csstools/color-helpers/-/color-helpers-5.1.0.tgz",
+      "integrity": "sha512-S11EXWJyy0Mz5SYvRmY8nJYTFFd1LCNV+7cXyAgQtOOuzb4EsgfqDufL+9esx72/eLhsRdGZwaldu/h+E4t4BA==",
+      "dev": true,
+      "funding": [
+        {
+          "type": "github",
+          "url": "https://github.com/sponsors/csstools"
+        },
+        {
+          "type": "opencollective",
+          "url": "https://opencollective.com/csstools"
+        }
+      ],
+      "license": "MIT-0",
+      "engines": {
+        "node": ">=18"
+      }
+    },
+    "node_modules/@csstools/css-calc": {
+      "version": "2.1.4",
+      "resolved": "https://registry.npmjs.org/@csstools/css-calc/-/css-calc-2.1.4.tgz",
+      "integrity": "sha512-3N8oaj+0juUw/1H3YwmDDJXCgTB1gKU6Hc/bB502u9zR0q2vd786XJH9QfrKIEgFlZmhZiq6epXl4rHqhzsIgQ==",
+      "dev": true,
+      "funding": [
+        {
+          "type": "github",
+          "url": "https://github.com/sponsors/csstools"
+        },
+        {
+          "type": "opencollective",
+          "url": "https://opencollective.com/csstools"
+        }
+      ],
+      "license": "MIT",
+      "engines": {
+        "node": ">=18"
+      },
+      "peerDependencies": {
+        "@csstools/css-parser-algorithms": "^3.0.5",
+        "@csstools/css-tokenizer": "^3.0.4"
+      }
+    },
+    "node_modules/@csstools/css-color-parser": {
+      "version": "3.1.0",
+      "resolved": "https://registry.npmjs.org/@csstools/css-color-parser/-/css-color-parser-3.1.0.tgz",
+      "integrity": "sha512-nbtKwh3a6xNVIp/VRuXV64yTKnb1IjTAEEh3irzS+HkKjAOYLTGNb9pmVNntZ8iVBHcWDA2Dof0QtPgFI1BaTA==",
+      "dev": true,
+      "funding": [
+        {
+          "type": "github",
+          "url": "https://github.com/sponsors/csstools"
+        },
+        {
+          "type": "opencollective",
+          "url": "https://opencollective.com/csstools"
+        }
+      ],
+      "license": "MIT",
+      "dependencies": {
+        "@csstools/color-helpers": "^5.1.0",
+        "@csstools/css-calc": "^2.1.4"
+      },
+      "engines": {
+        "node": ">=18"
+      },
+      "peerDependencies": {
+        "@csstools/css-parser-algorithms": "^3.0.5",
+        "@csstools/css-tokenizer": "^3.0.4"
+      }
+    },
+    "node_modules/@csstools/css-parser-algorithms": {
+      "version": "3.0.5",
+      "resolved": "https://registry.npmjs.org/@csstools/css-parser-algorithms/-/css-parser-algorithms-3.0.5.tgz",
+      "integrity": "sha512-DaDeUkXZKjdGhgYaHNJTV9pV7Y9B3b644jCLs9Upc3VeNGg6LWARAT6O+Q+/COo+2gg/bM5rhpMAtf70WqfBdQ==",
+      "dev": true,
+      "funding": [
+        {
+          "type": "github",
+          "url": "https://github.com/sponsors/csstools"
+        },
+        {
+          "type": "opencollective",
+          "url": "https://opencollective.com/csstools"
+        }
+      ],
+      "license": "MIT",
+      "engines": {
+        "node": ">=18"
+      },
+      "peerDependencies": {
+        "@csstools/css-tokenizer": "^3.0.4"
+      }
+    },
+    "node_modules/@csstools/css-tokenizer": {
+      "version": "3.0.4",
+      "resolved": "https://registry.npmjs.org/@csstools/css-tokenizer/-/css-tokenizer-3.0.4.tgz",
+      "integrity": "sha512-Vd/9EVDiu6PPJt9yAh6roZP6El1xHrdvIVGjyBsHR0RYwNHgL7FJPyIIW4fANJNG6FtyZfvlRPpFI4ZM/lubvw==",
+      "dev": true,
+      "funding": [
+        {
+          "type": "github",
+          "url": "https://github.com/sponsors/csstools"
+        },
+        {
+          "type": "opencollective",
+          "url": "https://opencollective.com/csstools"
+        }
+      ],
+      "license": "MIT",
+      "engines": {
+        "node": ">=18"
+      }
+    },
     "node_modules/@esbuild/aix-ppc64": {
       "version": "0.25.12",
       "resolved": "https://registry.npmjs.org/@esbuild/aix-ppc64/-/aix-ppc64-0.25.12.tgz",
@@ -1452,6 +1610,102 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/@testing-library/dom": {
+      "version": "10.4.1",
+      "resolved": "https://registry.npmjs.org/@testing-library/dom/-/dom-10.4.1.tgz",
+      "integrity": "sha512-o4PXJQidqJl82ckFaXUeoAW+XysPLauYI43Abki5hABd853iMhitooc6znOnczgbTYmEP6U6/y1ZyKAIsvMKGg==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@babel/code-frame": "^7.10.4",
+        "@babel/runtime": "^7.12.5",
+        "@types/aria-query": "^5.0.1",
+        "aria-query": "5.3.0",
+        "dom-accessibility-api": "^0.5.9",
+        "lz-string": "^1.5.0",
+        "picocolors": "1.1.1",
+        "pretty-format": "^27.0.2"
+      },
+      "engines": {
+        "node": ">=18"
+      }
+    },
+    "node_modules/@testing-library/jest-dom": {
+      "version": "6.9.1",
+      "resolved": "https://registry.npmjs.org/@testing-library/jest-dom/-/jest-dom-6.9.1.tgz",
+      "integrity": "sha512-zIcONa+hVtVSSep9UT3jZ5rizo2BsxgyDYU7WFD5eICBE7no3881HGeb/QkGfsJs6JTkY1aQhT7rIPC7e+0nnA==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@adobe/css-tools": "^4.4.0",
+        "aria-query": "^5.0.0",
+        "css.escape": "^1.5.1",
+        "dom-accessibility-api": "^0.6.3",
+        "picocolors": "^1.1.1",
+        "redent": "^3.0.0"
+      },
+      "engines": {
+        "node": ">=14",
+        "npm": ">=6",
+        "yarn": ">=1"
+      }
+    },
+    "node_modules/@testing-library/jest-dom/node_modules/dom-accessibility-api": {
+      "version": "0.6.3",
+      "resolved": "https://registry.npmjs.org/dom-accessibility-api/-/dom-accessibility-api-0.6.3.tgz",
+      "integrity": "sha512-7ZgogeTnjuHbo+ct10G9Ffp0mif17idi0IyWNVA/wcwcm7NPOD/WEHVP3n7n3MhXqxoIYm8d6MuZohYWIZ4T3w==",
+      "dev": true,
+      "license": "MIT"
+    },
+    "node_modules/@testing-library/react": {
+      "version": "16.3.2",
+      "resolved": "https://registry.npmjs.org/@testing-library/react/-/react-16.3.2.tgz",
+      "integrity": "sha512-XU5/SytQM+ykqMnAnvB2umaJNIOsLF3PVv//1Ew4CTcpz0/BRyy/af40qqrt7SjKpDdT1saBMc42CUok5gaw+g==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@babel/runtime": "^7.12.5"
+      },
+      "engines": {
+        "node": ">=18"
+      },
+      "peerDependencies": {
+        "@testing-library/dom": "^10.0.0",
+        "@types/react": "^18.0.0 || ^19.0.0",
+        "@types/react-dom": "^18.0.0 || ^19.0.0",
+        "react": "^18.0.0 || ^19.0.0",
+        "react-dom": "^18.0.0 || ^19.0.0"
+      },
+      "peerDependenciesMeta": {
+        "@types/react": {
+          "optional": true
+        },
+        "@types/react-dom": {
+          "optional": true
+        }
+      }
+    },
+    "node_modules/@testing-library/user-event": {
+      "version": "14.6.1",
+      "resolved": "https://registry.npmjs.org/@testing-library/user-event/-/user-event-14.6.1.tgz",
+      "integrity": "sha512-vq7fv0rnt+QTXgPxr5Hjc210p6YKq2kmdziLgnsZGgLJ9e6VAShx1pACLuRjd/AS/sr7phAR58OIIpf0LlmQNw==",
+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": ">=12",
+        "npm": ">=6"
+      },
+      "peerDependencies": {
+        "@testing-library/dom": ">=7.21.4"
+      }
+    },
+    "node_modules/@types/aria-query": {
+      "version": "5.0.4",
+      "resolved": "https://registry.npmjs.org/@types/aria-query/-/aria-query-5.0.4.tgz",
+      "integrity": "sha512-rfT93uj5s0PRL7EzccGMs3brplhcrghnDoV26NqKhCAS1hVo+WdNsPvE/yb6ilfr5hi2MEk6d5EWJTKdxg8jVw==",
+      "dev": true,
+      "license": "MIT"
+    },
     "node_modules/@types/babel__core": {
       "version": "7.20.5",
       "resolved": "https://registry.npmjs.org/@types/babel__core/-/babel__core-7.20.5.tgz",
@@ -1746,6 +2000,16 @@
         "url": "https://github.com/sponsors/epoberezkin"
       }
     },
+    "node_modules/ansi-regex": {
+      "version": "5.0.1",
+      "resolved": "https://registry.npmjs.org/ansi-regex/-/ansi-regex-5.0.1.tgz",
+      "integrity": "sha512-quJQXlTSUGL2LH9SUXo8VwsY4soanhgo6LNSm84E1LBcE8s3O0wpdiRzyR9z/ZZJMlMWv37qOOb9pdJlMUEKFQ==",
+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": ">=8"
+      }
+    },
     "node_modules/ansi-styles": {
       "version": "4.3.0",
       "resolved": "https://registry.npmjs.org/ansi-styles/-/ansi-styles-4.3.0.tgz",
@@ -1769,6 +2033,16 @@
       "dev": true,
       "license": "Python-2.0"
     },
+    "node_modules/aria-query": {
+      "version": "5.3.0",
+      "resolved": "https://registry.npmjs.org/aria-query/-/aria-query-5.3.0.tgz",
+      "integrity": "sha512-b0P0sZPKtyu8HkeRAfCq0IfURZK+SuwMjY1UXGBU27wpAiTwQAIlq56IbIO+ytk/JjS1fMR14ee5WBBfKi5J6A==",
+      "dev": true,
+      "license": "Apache-2.0",
+      "dependencies": {
+        "dequal": "^2.0.3"
+      }
+    },
     "node_modules/assertion-error": {
       "version": "2.0.1",
       "resolved": "https://registry.npmjs.org/assertion-error/-/assertion-error-2.0.1.tgz",
@@ -2026,6 +2300,41 @@
         "node": ">= 8"
       }
     },
+    "node_modules/css.escape": {
+      "version": "1.5.1",
+      "resolved": "https://registry.npmjs.org/css.escape/-/css.escape-1.5.1.tgz",
+      "integrity": "sha512-YUifsXXuknHlUsmlgyY0PKzgPOr7/FjCePfHNt0jxm83wHZi44VDMQ7/fGNkjY3/jV1MC+1CmZbaHzugyeRtpg==",
+      "dev": true,
+      "license": "MIT"
+    },
+    "node_modules/cssstyle": {
+      "version": "4.6.0",
+      "resolved": "https://registry.npmjs.org/cssstyle/-/cssstyle-4.6.0.tgz",
+      "integrity": "sha512-2z+rWdzbbSZv6/rhtvzvqeZQHrBaqgogqt85sqFNbabZOuFbCVFb8kPeEtZjiKkbrm395irpNKiYeFeLiQnFPg==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@asamuzakjp/css-color": "^3.2.0",
+        "rrweb-cssom": "^0.8.0"
+      },
+      "engines": {
+        "node": ">=18"
+      }
+    },
+    "node_modules/data-urls": {
+      "version": "5.0.0",
+      "resolved": "https://registry.npmjs.org/data-urls/-/data-urls-5.0.0.tgz",
+      "integrity": "sha512-ZYP5VBHshaDAiVZxjbRVcFJpc+4xGgT0bK3vzy1HLN8jTO975HEbuYzZJcHoQEY5K1a0z8YayJkyVETa08eNTg==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "whatwg-mimetype": "^4.0.0",
+        "whatwg-url": "^14.0.0"
+      },
+      "engines": {
+        "node": ">=18"
+      }
+    },
     "node_modules/debug": {
       "version": "4.4.3",
       "resolved": "https://registry.npmjs.org/debug/-/debug-4.4.3.tgz",
@@ -2043,6 +2352,13 @@
         }
       }
     },
+    "node_modules/decimal.js": {
+      "version": "10.6.0",
+      "resolved": "https://registry.npmjs.org/decimal.js/-/decimal.js-10.6.0.tgz",
+      "integrity": "sha512-YpgQiITW3JXGntzdUmyUR1V812Hn8T1YVXhCu+wO3OpS4eU9l4YdD3qjyiKdV6mvV29zapkMeD390UVEf2lkUg==",
+      "dev": true,
+      "license": "MIT"
+    },
     "node_modules/deep-is": {
       "version": "0.1.4",
       "resolved": "https://registry.npmjs.org/deep-is/-/deep-is-0.1.4.tgz",
@@ -2059,6 +2375,23 @@
         "node": ">=0.4.0"
       }
     },
+    "node_modules/dequal": {
+      "version": "2.0.3",
+      "resolved": "https://registry.npmjs.org/dequal/-/dequal-2.0.3.tgz",
+      "integrity": "sha512-0je+qPKHEMohvfRTCEo3CrPG6cAzAYgmzKyxRiYSSDkS6eGJdyVJm7WaYA5ECaAD9wLB2T4EEeymA5aFVcYXCA==",
+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": ">=6"
+      }
+    },
+    "node_modules/dom-accessibility-api": {
+      "version": "0.5.16",
+      "resolved": "https://registry.npmjs.org/dom-accessibility-api/-/dom-accessibility-api-0.5.16.tgz",
+      "integrity": "sha512-X7BJ2yElsnOJ30pZF4uIIDfBEVgF4XEBxL9Bxhy6dnrm5hkzqmsWHGTiHqRiITNhMyFLyAiWndIJP7Z1NTteDg==",
+      "dev": true,
+      "license": "MIT"
+    },
     "node_modules/dunder-proto": {
       "version": "1.0.1",
       "resolved": "https://registry.npmjs.org/dunder-proto/-/dunder-proto-1.0.1.tgz",
@@ -2080,6 +2413,19 @@
       "dev": true,
       "license": "ISC"
     },
+    "node_modules/entities": {
+      "version": "6.0.1",
+      "resolved": "https://registry.npmjs.org/entities/-/entities-6.0.1.tgz",
+      "integrity": "sha512-aN97NXWF6AWBTahfVOIrB/NShkzi5H7F9r1s9mD3cDj4Ko5f2qhhVoYMibXF7GlLveb/D2ioWay8lxI97Ven3g==",
+      "dev": true,
+      "license": "BSD-2-Clause",
+      "engines": {
+        "node": ">=0.12"
+      },
+      "funding": {
+        "url": "https://github.com/fb55/entities?sponsor=1"
+      }
+    },
     "node_modules/es-define-property": {
       "version": "1.0.1",
       "resolved": "https://registry.npmjs.org/es-define-property/-/es-define-property-1.0.1.tgz",
@@ -2668,6 +3014,19 @@
         "node": ">= 0.4"
       }
     },
+    "node_modules/html-encoding-sniffer": {
+      "version": "4.0.0",
+      "resolved": "https://registry.npmjs.org/html-encoding-sniffer/-/html-encoding-sniffer-4.0.0.tgz",
+      "integrity": "sha512-Y22oTqIU4uuPgEemfz7NDJz6OeKf12Lsu+QC+s3BVpda64lTiMYCyGwg5ki4vFxkMwQdeZDl2adZoqUgdFuTgQ==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "whatwg-encoding": "^3.1.1"
+      },
+      "engines": {
+        "node": ">=18"
+      }
+    },
     "node_modules/html-escaper": {
       "version": "2.0.2",
       "resolved": "https://registry.npmjs.org/html-escaper/-/html-escaper-2.0.2.tgz",
@@ -2675,6 +3034,30 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/http-proxy-agent": {
+      "version": "7.0.2",
+      "resolved": "https://registry.npmjs.org/http-proxy-agent/-/http-proxy-agent-7.0.2.tgz",
+      "integrity": "sha512-T1gkAiYYDWYx3V5Bmyu7HcfcvL7mUrTWiM6yOfa3PIphViJ/gFPbvidQ+veqSOHci/PxBcDabeUNCzpOODJZig==",
+      "dev": true,
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+      "license": "MIT",
+      "engines": {
+        "node": ">=10.0.0"
+      },
+      "peerDependencies": {
+        "bufferutil": "^4.0.1",
+        "utf-8-validate": ">=5.0.2"
+      },
+      "peerDependenciesMeta": {
+        "bufferutil": {
+          "optional": true
+        },
+        "utf-8-validate": {
+          "optional": true
+        }
+      }
+    },
+    "node_modules/xml-name-validator": {
+      "version": "5.0.0",
+      "resolved": "https://registry.npmjs.org/xml-name-validator/-/xml-name-validator-5.0.0.tgz",
+      "integrity": "sha512-EvGK8EJ3DhaHfbRlETOWAS5pO9MZITeauHKJyb8wyajUfQUenkIg2MvLDTZ4T/TgIcm3HU0TFBgWWboAZ30UHg==",
+      "dev": true,
+      "license": "Apache-2.0",
+      "engines": {
+        "node": ">=18"
+      }
+    },
+    "node_modules/xmlchars": {
+      "version": "2.2.0",
+      "resolved": "https://registry.npmjs.org/xmlchars/-/xmlchars-2.2.0.tgz",
+      "integrity": "sha512-JZnDKK8B0RCDw84FNdDAIpZK+JuJw+s7Lz8nksI7SIuU3UXJJslUthsi+uWBUYOwPFwW7W7PRLRfUKpxjtjFCw==",
+      "dev": true,
+      "license": "MIT"
+    },
     "node_modules/yallist": {
       "version": "3.1.1",
       "resolved": "https://registry.npmjs.org/yallist/-/yallist-3.1.1.tgz",

frontend/package.json

@@ -22,11 +22,16 @@
   "devDependencies": {
     "@eslint/js": "^9.17.0",
     "@playwright/test": "1.49.1",
+    "@testing-library/dom": "^10.4.0",
+    "@testing-library/jest-dom": "^6.6.3",
+    "@testing-library/react": "^16.1.0",
+    "@testing-library/user-event": "^14.5.2",
     "@vitejs/plugin-react": "^4.3.4",
     "@vitest/coverage-v8": "^4.1.10",
     "eslint": "^9.17.0",
     "eslint-plugin-react-hooks": "^5.1.0",
     "globals": "^15.14.0",
+    "jsdom": "^26.0.0",
     "vite": "^6.0.7",
     "vitest": "^4.1.10"
   }

frontend/src/components/Badge.test.jsx

@@ -0,0 +1,28 @@
+// @vitest-environment jsdom
+import { describe, it, expect } from 'vitest'
+import { render, screen } from '@testing-library/react'
+import Badge from './Badge.jsx'
+
+// 이 파일이 하는 일: Badge 컴포넌트가 "코드값 → 한국어 라벨 + 색"을 올바로 그리는지,
+//   그리고 표에 없는 값이 와도 죽지 않고 안전하게 처리하는지(폴백) 검증한다.
+
+describe('Badge', () => {
+  it('알려진 상태값을 한국어 라벨로 보여준다', () => {
+    render(<Badge value="PASSED" />)
+    expect(screen.getByText('통과')).toBeInTheDocument()
+  })
+
+  it('상태에 맞는 색 클래스를 붙인다', () => {
+    render(<Badge value="SUBMITTED" />)
+    const badge = screen.getByText('제출됨')
+    expect(badge).toHaveClass('badge', 'badge-amber')
+  })
+
+  it('변환표에 없는 값이 와도 죽지 않고 원래 값을 그대로 보여준다(폴백)', () => {
+    // 학습 포인트: 서버에 새 상태가 생겨도 화면이 깨지지 않아야 한다는 "방어적 기본값"을 못 박는다.
+    render(<Badge value="ALIEN_STATUS" />)
+    const badge = screen.getByText('ALIEN_STATUS')
+    expect(badge).toBeInTheDocument()
+    expect(badge).toHaveClass('badge-primary') // 기본 색으로 대체
+  })
+})

frontend/src/components/CodeEditor.test.jsx

@@ -0,0 +1,65 @@
+// @vitest-environment jsdom
+import { describe, it, expect, vi } from 'vitest'
+import { useState } from 'react'
+import { render, screen, fireEvent } from '@testing-library/react'
+import userEvent from '@testing-library/user-event'
+import CodeEditor from './CodeEditor.jsx'
+
+// 이 파일이 하는 일: 코드 에디터의 "제어된 입력", 줄번호, Tab 들여쓰기(+커서 위치 버그 수정)를
+//   실제 DOM(jsdom)에서 눌러 보며 검증한다.
+
+// CodeEditor는 제어 컴포넌트(value를 부모가 쥔다)라, 실제처럼 상태를 쥔 껍데기로 감싸 테스트한다.
+function Harness({ initial = '', minRows }) {
+  const [value, setValue] = useState(initial)
+  return <CodeEditor value={value} onChange={setValue} minRows={minRows} />
+}
+
+describe('CodeEditor', () => {
+  it('전달받은 값을 textarea에 보여준다', () => {
+    render(<CodeEditor value="print(1)" onChange={() => {}} />)
+    expect(screen.getByRole('textbox')).toHaveValue('print(1)')
+  })
+
+  it('타이핑하면 부모 상태가 갱신돼 글자가 누적된다(제어 왕복)', async () => {
+    const user = userEvent.setup()
+    render(<Harness />)
+    const textarea = screen.getByRole('textbox')
+    await user.type(textarea, 'hello')
+    expect(textarea).toHaveValue('hello')
+  })
+
+  it('줄번호는 최소 minRows개를 보장한다(빈 값이어도 창이 안 쪼그라듦)', () => {
+    const { container } = render(<CodeEditor value="" onChange={() => {}} minRows={5} />)
+    const lines = container.querySelectorAll('.code-editor__gutter > div')
+    expect(lines).toHaveLength(5)
+  })
+
+  it('줄 수가 minRows보다 많으면 줄 수만큼 줄번호가 늘어난다', () => {
+    const { container } = render(<CodeEditor value={'a\nb\nc\nd'} onChange={() => {}} minRows={2} />)
+    const lines = container.querySelectorAll('.code-editor__gutter > div')
+    expect(lines).toHaveLength(4) // 4줄 > minRows 2
+  })
+
+  it('Tab을 누르면 브라우저 기본동작 대신 공백 2칸을 커서 위치에 끼워 넣는다', () => {
+    const onChange = vi.fn()
+    render(<CodeEditor value="ab" onChange={onChange} />)
+    const textarea = screen.getByRole('textbox')
+    textarea.setSelectionRange(1, 1) // 커서를 a와 b 사이에 둔다
+    fireEvent.keyDown(textarea, { key: 'Tab' })
+    expect(onChange).toHaveBeenCalledWith('a  b') // a + 공백2 + b
+  })
+
+  it('텍스트를 선택한 채 Tab을 누르면 선택 영역이 공백 2칸으로 치환되고 커서가 그 뒤에 온다', async () => {
+    // 학습 포인트: 예전엔 커서를 selectionEnd+2로 잘못 계산해, 선택 후 Tab이면 커서가 밀렸다.
+    //   올바른 값은 selectionStart+2. 이 회귀를 못 박는 테스트다.
+    render(<Harness initial="abcd" />)
+    const textarea = screen.getByRole('textbox')
+    textarea.setSelectionRange(1, 3) // 'bc'를 선택
+    fireEvent.keyDown(textarea, { key: 'Tab' })
+    expect(textarea).toHaveValue('a  d') // 선택('bc')이 공백 2칸으로 치환
+
+    await new Promise((resolve) => requestAnimationFrame(resolve)) // 커서 이동은 다음 프레임에
+    expect(textarea.selectionStart).toBe(3) // selectionStart(1) + 2  — 버그판이면 5였다
+    expect(textarea.selectionEnd).toBe(3)
+  })
+})

frontend/src/components/ProgressBar.test.jsx

@@ -0,0 +1,30 @@
+// @vitest-environment jsdom
+import { describe, it, expect } from 'vitest'
+import { render, screen } from '@testing-library/react'
+import ProgressBar from './ProgressBar.jsx'
+
+// 이 파일이 하는 일: 진행률 계산(반올림)과 0 나눗셈 방어, 막대 너비를 검증한다.
+
+describe('ProgressBar', () => {
+  it('진행률을 백분율로 계산해 표시한다', () => {
+    render(<ProgressBar value={3} total={4} />)
+    expect(screen.getByText('3 / 4 (75%)')).toBeInTheDocument()
+  })
+
+  it('소수점은 반올림한다', () => {
+    render(<ProgressBar value={1} total={3} />) // 33.33... → 33
+    expect(screen.getByText('1 / 3 (33%)')).toBeInTheDocument()
+  })
+
+  it('total이 0이면 NaN이 아니라 0%를 보여준다(0 나눗셈 방어)', () => {
+    // 학습 포인트: total/0은 NaN이 되어 "NaN%"가 찍히는 사고 — 이 방어를 못 박는다.
+    render(<ProgressBar value={0} total={0} />)
+    expect(screen.getByText('0 / 0 (0%)')).toBeInTheDocument()
+  })
+
+  it('채워진 막대의 너비가 진행률과 같다', () => {
+    const { container } = render(<ProgressBar value={1} total={4} />) // 25%
+    const fill = container.querySelector('.progress-fill')
+    expect(fill).toHaveStyle({ width: '25%' })
+  })
+})

frontend/src/test/setup.js

@@ -0,0 +1,15 @@
+// 이 파일이 하는 일: 컴포넌트 테스트가 시작되기 전에 한 번 실행되는 준비 코드.
+//
+// 학습 포인트: @testing-library/jest-dom은 "화면 요소용 단언(matcher)"을 추가한다.
+//   예: expect(el).toBeInTheDocument(), toHaveClass(...), toHaveValue(...).
+//   이걸 불러와 둬야 컴포넌트 테스트에서 이런 읽기 쉬운 단언들을 쓸 수 있다.
+import '@testing-library/jest-dom/vitest'
+import { afterEach } from 'vitest'
+import { cleanup } from '@testing-library/react'
+
+// 학습 포인트: 각 테스트가 그린 화면을 다음 테스트로 넘기지 않도록, 매 테스트 후 DOM을 비운다.
+//   (vitest globals를 안 켰을 때 Testing Library의 자동 정리가 등록되지 않아 직접 걸어 준다.
+//    안 하면 textarea 같은 요소가 쌓여 getByRole이 "여러 개 발견"으로 실패한다.)
+afterEach(() => {
+  cleanup()
+})

frontend/vite.config.js

@@ -21,6 +21,10 @@ export default defineConfig({
     // 학습 포인트: vitest는 기본으로 *.spec.js도 잡는데, e2e/의 Playwright 스펙(*.spec.js)은
     //   브라우저 러너(Playwright)로만 돌아야 한다. 여기서 범위를 src로 좁혀 둘을 분리한다.
     include: ['src/**/*.{test,spec}.{js,jsx}'],
+    // 컴포넌트 테스트가 시작 전에 화면용 단언(jest-dom)을 불러오게 한다.
+    // 환경(jsdom vs node)은 파일 상단의 // @vitest-environment 주석으로 파일별로 정한다
+    //   — 순수 로직 테스트(runSql)는 node 그대로 두고, 컴포넌트 테스트만 jsdom을 쓴다.
+    setupFiles: ['./src/test/setup.js'],
     coverage: {
       provider: 'v8',
       include: ['src/lib/**'],