Erro na preparação do ambiente.

npm audit fix

npm WARN deprecated chokidar@2.1.8: Chokidar 2 will break on node v14+. Upgrade to chokidar 3 with 15x less dependencies.
npm WARN deprecated fsevents@1.2.13: fsevents 1 will break on node v14+ and could be using insecure binaries. Upgrade to fsevents 2.
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@^1.2.7 (node_modules/webpack-dev-server/node_modules/chokidar/node_modules/fsevents):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@1.2.13: wanted {"os":"darwin","arch":"any"} (current: {"os":"linux","arch":"x64"})
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@2.1.3 (node_modules/fsevents):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@2.1.3: wanted {"os":"darwin","arch":"any"} (current: {"os":"linux","arch":"x64"})
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@1.2.13 (node_modules/jest-haste-map/node_modules/fsevents):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@1.2.13: wanted {"os":"darwin","arch":"any"} (current: {"os":"linux","arch":"x64"})
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@1.2.13 (node_modules/watchpack-chokidar2/node_modules/fsevents):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@1.2.13: wanted {"os":"darwin","arch":"any"} (current: {"os":"linux","arch":"x64"})

+ axios@0.21.1
added 9 packages from 23 contributors, removed 10 packages, updated 9 packages and moved 1 package in 14.927s

54 packages are looking for funding
  run `npm fund` for details

fixed 4725 of 4730 vulnerabilities in 1602 scanned packages
  5 vulnerabilities

 required manual review and could not be updated

-

npm run serve

> testing@0.1.0 serve /home/fredo/Development/Javascript/Vue.js: Testes unitários automatizados com Jest/vue-test-master
> vue-cli-service serve

sh: 1: vue-cli-service: not found
npm ERR! code ELIFECYCLE
npm ERR! syscall spawn
npm ERR! file sh
npm ERR! errno ENOENT
npm ERR! testing@0.1.0 serve: `vue-cli-service serve`
npm ERR! spawn ENOENT
npm ERR! 
npm ERR! Failed at the testing@0.1.0 serve script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR!     /home/fredo/.npm/_logs/2021-04-07T17_53_02_028Z-debug.log

-

2021-04-07T17_53_02_028Z-debug.log

0 info it worked if it ends with ok
1 verbose cli [ '/usr/bin/node', '/usr/bin/npm', 'run', 'serve' ]
2 info using npm@6.14.4
3 info using node@v10.19.0
4 verbose run-script [ 'preserve', 'serve', 'postserve' ]
5 info lifecycle testing@0.1.0~preserve: testing@0.1.0
6 info lifecycle testing@0.1.0~serve: testing@0.1.0
7 verbose lifecycle testing@0.1.0~serve: unsafe-perm in lifecycle true
8 verbose lifecycle testing@0.1.0~serve: PATH: /usr/share/npm/node_modules/npm-lifecycle/node-gyp-bin:/home/fredo/Development/Javascript/Vue.js: Testes unitários automatizados com Jest/vue-test-master/node_modules/.bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/home/fredo/.dotnet/tools
9 verbose lifecycle testing@0.1.0~serve: CWD: /home/fredo/Development/Javascript/Vue.js: Testes unitários automatizados com Jest/vue-test-master
10 silly lifecycle testing@0.1.0~serve: Args: [ '-c', 'vue-cli-service serve' ]
11 info lifecycle testing@0.1.0~serve: Failed to exec serve script
12 verbose stack Error: testing@0.1.0 serve: `vue-cli-service serve`
12 verbose stack spawn ENOENT
12 verbose stack     at ChildProcess.<anonymous> (/usr/share/npm/node_modules/npm-lifecycle/lib/spawn.js:48:18)
12 verbose stack     at ChildProcess.emit (events.js:198:13)
12 verbose stack     at maybeClose (internal/child_process.js:982:16)
12 verbose stack     at Process.ChildProcess._handle.onexit (internal/child_process.js:259:5)
13 verbose pkgid testing@0.1.0
14 verbose cwd /home/fredo/Development/Javascript/Vue.js: Testes unitários automatizados com Jest/vue-test-master
15 verbose Linux 5.8.0-48-generic
16 verbose argv "/usr/bin/node" "/usr/bin/npm" "run" "serve"
17 verbose node v10.19.0
18 verbose npm  v6.14.4
19 error code ELIFECYCLE
20 error syscall spawn
21 error file sh
22 error errno ENOENT
23 error testing@0.1.0 serve: `vue-cli-service serve`
23 error spawn ENOENT
24 error Failed at the testing@0.1.0 serve script.
24 error This is probably not a problem with npm. There is likely additional logging output above.
25 verbose exit [ 1, true ]

Olá, Frederico!

Vamos tentar novamente?

Baixe novamente o projeto inicial aqui num local diferente. Após descompactar o projeto, vamos pedir ao npm para instalar as dependências:

npm install

e em seguida:

npm run serve

Pude perceber que por algum motivo a versão do node que está instalada é a 10.19. Caso o problema persista, você pode usar o nvm para configurar a versão mais recente do node (a versão LTS mais recente, na data que respondo, é a 14.16.1) e então refazer esses passos.

Olá, Mesmo após atualização da versão do node erro persiste:

node --version

v14.16.1

-

npm install

npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@1.2.11 (node_modules/fsevents):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@1.2.11: wanted {"os":"darwin","arch":"any"} (current: {"os":"linux","arch":"x64"})

audited 1284 packages in 12.373s

39 packages are looking for funding
  run `npm fund` for details

found 298 vulnerabilities (272 low, 7 moderate, 19 high)
  run `npm audit fix` to fix them, or `npm audit` for details

-

npm run serve

> projeto@0.1.0 serve /home/fredo/Development/Javascript/Alura/Vue.js: Testes unitários automatizados com Jest/auth-vue-vuex-48dd3dd2848ff6df4ed6dca43fa9dee1361b46db
> vue-cli-service serve

sh: 1: vue-cli-service: not found
npm ERR! code ELIFECYCLE
npm ERR! syscall spawn
npm ERR! file sh
npm ERR! errno ENOENT
npm ERR! projeto@0.1.0 serve: `vue-cli-service serve`
npm ERR! spawn ENOENT
npm ERR! 
npm ERR! Failed at the projeto@0.1.0 serve script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR!     /home/fredo/.npm/_logs/2021-04-11T19_50_33_896Z-debug.log

-

 /home/fredo/.npm/_logs/2021-04-11T19_50_33_896Z-debug.log

0 info it worked if it ends with ok
1 verbose cli [
1 verbose cli   '/home/fredo/.nvm/versions/node/v14.16.1/bin/node',
1 verbose cli   '/home/fredo/.nvm/versions/node/v14.16.1/bin/npm',
1 verbose cli   'run',
1 verbose cli   'serve'
1 verbose cli ]
2 info using npm@6.14.12
3 info using node@v14.16.1
4 verbose run-script [ 'preserve', 'serve', 'postserve' ]
5 info lifecycle projeto@0.1.0~preserve: projeto@0.1.0
6 info lifecycle projeto@0.1.0~serve: projeto@0.1.0
7 verbose lifecycle projeto@0.1.0~serve: unsafe-perm in lifecycle true
8 verbose lifecycle projeto@0.1.0~serve: PATH: /home/fredo/.nvm/versions/node/v14.16.1/lib/node_modules/npm/node_modules/npm-lifecycle/node-gyp-bin:/home/fredo/Development/Javascript/Alura/Vue.js: Testes unitários automatizados com Jest/auth-vue-vuex-48dd3dd2848ff6df4ed6dca43fa9dee1361b46db/node_modules/.bin:/home/fredo/.nvm/versions/node/v14.16.1/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/home/fredo/.dotnet/tools
9 verbose lifecycle projeto@0.1.0~serve: CWD: /home/fredo/Development/Javascript/Alura/Vue.js: Testes unitários automatizados com Jest/auth-vue-vuex-48dd3dd2848ff6df4ed6dca43fa9dee1361b46db
10 silly lifecycle projeto@0.1.0~serve: Args: [ '-c', 'vue-cli-service serve' ]
11 info lifecycle projeto@0.1.0~serve: Failed to exec serve script
12 verbose stack Error: projeto@0.1.0 serve: `vue-cli-service serve`
12 verbose stack spawn ENOENT
12 verbose stack     at ChildProcess.<anonymous> (/home/fredo/.nvm/versions/node/v14.16.1/lib/node_modules/npm/node_modules/npm-lifecycle/lib/spawn.js:48:18)
12 verbose stack     at ChildProcess.emit (events.js:315:20)
12 verbose stack     at maybeClose (internal/child_process.js:1048:16)
12 verbose stack     at Process.ChildProcess._handle.onexit (internal/child_process.js:288:5)
13 verbose pkgid projeto@0.1.0
14 verbose cwd /home/fredo/Development/Javascript/Alura/Vue.js: Testes unitários automatizados com Jest/auth-vue-vuex-48dd3dd2848ff6df4ed6dca43fa9dee1361b46db
15 verbose Linux 5.8.0-48-generic
16 verbose argv "/home/fredo/.nvm/versions/node/v14.16.1/bin/node" "/home/fredo/.nvm/versions/node/v14.16.1/bin/npm" "run" "serve"
17 verbose node v14.16.1
18 verbose npm  v6.14.12
19 error code ELIFECYCLE
20 error syscall spawn
21 error file sh
22 error errno ENOENT
23 error projeto@0.1.0 serve: `vue-cli-service serve`
23 error spawn ENOENT
24 error Failed at the projeto@0.1.0 serve script.
24 error This is probably not a problem with npm. There is likely additional logging output above.
25 verbose exit [ 1, true ]

Frederico, pode confirmar pra mim a versão do seu Ubunto?

O erro que vc compartilhou é que o vue-cli-service não foi encontrado. Pode verificar tb se ele existe na pasta node_modules/@vue/cli-service ?