diff --git a/.eslintrc.yml b/.eslintrc.yml
index 39ace7e..d0dcfc2 100644
--- a/.eslintrc.yml
+++ b/.eslintrc.yml
@@ -9,7 +9,6 @@ parserOptions:
 rules:
   indent: ["warn", 2]
   max-len: ["warn", 100]
-  no-console: 0
   no-undef: "error"
   no-unused-vars: ["error", {"varsIgnorePattern": "^_"}]
   no-use-before-define: 0
diff --git a/.github/workflows/action.yml b/.github/workflows/action.yml
index 360c812..ce652cb 100644
--- a/.github/workflows/action.yml
+++ b/.github/workflows/action.yml
@@ -46,7 +46,7 @@ jobs:
         id: setup-beam
         uses: ./
         with:
-          version-file: __tests__/.tool-versions
+          version-file: test/.tool-versions
           version-type: strict
 
   unit_tests_windows:
diff --git a/.github/workflows/hexpm-mirrors.yml b/.github/workflows/hexpm-mirrors.yml
index b87d1da..2bc5493 100644
--- a/.github/workflows/hexpm-mirrors.yml
+++ b/.github/workflows/hexpm-mirrors.yml
@@ -35,24 +35,3 @@ jobs:
             https://mirror.invalid
             https://cdn.jsdelivr.net/hex
             https://builds.hex.pm
-
-  test-invalid-mirror:
-    name: Test errors with mirror
-    runs-on: ubuntu-22.04
-    steps:
-      - uses: actions/checkout@v3
-      - name: Use erlef/setup-beam
-        id: failing-setup-beam
-        uses: ./
-        continue-on-error: true
-        with:
-          otp-version: '24.3.4.6'
-          elixir-version: 'v1.13.4'
-          install-rebar: true
-          install-hex: true
-          hexpm-mirrors: https://mirror.invalid
-      - name: Report unexpected success
-        if: ${{ steps.failing-setup-beam.outcome == 'success' }}
-        run: |
-          echo "Action is expected to fail"
-          exit 1
diff --git a/.github/workflows/ubuntu.yml b/.github/workflows/ubuntu.yml
index 6e07fd1..b0b0638 100644
--- a/.github/workflows/ubuntu.yml
+++ b/.github/workflows/ubuntu.yml
@@ -53,7 +53,7 @@ jobs:
             os: 'ubuntu-latest'
           - elixir-version: 'v1.4'
             otp-version: '20'
-            rebar3-version: '3.6.0'
+            rebar3-version: '3.15.0'
             os: 'ubuntu-20.04'
           - elixir-version: 'v1.4'
             otp-version: '20'
@@ -165,23 +165,23 @@ jobs:
         if: ${{matrix.combo.elixir-version}}
       - name: Run Elixir/Mix project tests
         run: |
-          cd test-projects/elixir_mix
+          cd test/projects/elixir_mix
           mix deps.get
           mix test
         if: ${{matrix.combo.elixir-version}}
       - name: Run Erlang/rebar3 project tests
         run: |
-          cd test-projects/erlang_rebar3
+          cd test/projects/erlang_rebar3
           rebar3 ct
         if: ${{matrix.combo.rebar3-version}}
       - name: Format Gleam project (without installing Erlang/OTP)
         run: |
-          cd test-projects/gleam_gleam
+          cd test/projects/gleam_gleam
           gleam format
         if: ${{ matrix.combo.gleam-version && !matrix.combo.otp-version }}
       - name: Run Gleam project tests (without `rebar3`)
         run: |
-          cd test-projects/gleam_gleam
+          cd test/projects/gleam_gleam
           gleam test
         if: ${{ matrix.combo.gleam-version && matrix.combo.otp-version && !matrix.combo.rebar3-version }}
       - name: Run escript
diff --git a/.github/workflows/windows.yml b/.github/workflows/windows.yml
index 6f51869..350c770 100644
--- a/.github/workflows/windows.yml
+++ b/.github/workflows/windows.yml
@@ -79,7 +79,7 @@ jobs:
         if: ${{matrix.combo.rebar3-version}}
       - name: rebar3 from Rust
         run: |
-          cd test-projects/rust_rebar3_cmd
+          cd test/projects/rust_rebar3_cmd
           cargo test -- --nocapture
         if: ${{matrix.combo.rebar3-version}}
       - name: mix version and help (CLI)
@@ -90,13 +90,13 @@ jobs:
         if: ${{matrix.combo.elixir-version}}
       - name: Run Elixir/Mix project tests
         run: |
-          cd test-projects/elixir_mix
+          cd test/projects/elixir_mix
           mix deps.get
           mix test
         if: ${{matrix.combo.elixir-version}}
       - name: Run Erlang/rebar3 project tests
         run: |
-          cd test-projects/erlang_rebar3
+          cd test/projects/erlang_rebar3
           rebar3 ct
         if: ${{matrix.combo.rebar3-version}}
       - name: Run escript
diff --git a/.gitignore b/.gitignore
index cf5dea3..40e3512 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,3 @@
 node_modules/**
 dist/.github/workflows
-__tests__/.tool-versions
+test/.tool-versions
diff --git a/MATCHER_NOTICE.md b/MATCHER_NOTICE.md
index ab9ac8a..40d3f1f 100644
--- a/MATCHER_NOTICE.md
+++ b/MATCHER_NOTICE.md
@@ -1,6 +1,6 @@
 # Elixir Problem Matchers
 
-Elixir Problem Matchers in [elixir-matchers.json](.github/elixir-matchers.json)
+Elixir Problem Matchers in [elixir-matchers.json](matchers/elixir-matchers.json)
 are adapted from [here](https://github.com/fr1zle/vscode-elixir/blob/45eddb589acd7ac98e0c7305d1c2b24668ca709a/package.json#L70-L118),
 available under the [MIT license](https://github.com/fr1zle/vscode-elixir/blob/45eddb589acd7ac98e0c7305d1c2b24668ca709a/LICENSE.md):
 
diff --git a/.github/elixir-matchers.json b/dist/elixir-matchers.json
similarity index 100%
rename from .github/elixir-matchers.json
rename to dist/elixir-matchers.json
diff --git a/dist/index.js b/dist/index.js
index 8fd3f68..b110276 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -7303,13 +7303,11 @@ async function main() {
 
 async function installOTP(otpSpec, osVersion, hexMirrors) {
   const otpVersion = await getOTPVersion(otpSpec, osVersion, hexMirrors)
-  console.log(
-    `##[group]Installing Erlang/OTP ${otpVersion} - built on ${osVersion}`,
-  )
+  core.startGroup(`Installing Erlang/OTP ${otpVersion} - built on ${osVersion}`)
   await installer.installOTP(osVersion, otpVersion, hexMirrors)
   core.setOutput('otp-version', otpVersion)
   core.addPath(`${process.env.RUNNER_TEMP}/.setup-beam/otp/bin`)
-  console.log('##[endgroup]')
+  core.endGroup()
 
   return otpVersion
 }
@@ -7323,19 +7321,17 @@ async function maybeInstallElixir(elixirSpec, otpSpec, hexMirrors) {
       otpSpec,
       hexMirrors,
     )
-    console.log(`##[group]Installing Elixir ${elixirVersion}`)
+    core.startGroup(`Installing Elixir ${elixirVersion}`)
     await installer.installElixir(elixirVersion, hexMirrors)
     core.setOutput('elixir-version', elixirVersion)
     const disableProblemMatchers = getInput('disable_problem_matchers', false)
     if (disableProblemMatchers === 'false') {
-      const matchersPath = __nccwpck_require__.ab + ".github"
-      console.log(
-        `##[add-matcher]${path.join(matchersPath, 'elixir-matchers.json')}`,
-      )
+      const elixirMatchers = __nccwpck_require__.ab + "elixir-matchers.json"
+      core.info(`##[add-matcher]${elixirMatchers}`)
     }
     core.addPath(`${os.homedir()}/.mix/escripts`)
     core.addPath(`${process.env.RUNNER_TEMP}/.setup-beam/elixir/bin`)
-    console.log('##[endgroup]')
+    core.endGroup()
 
     installed = true
   }
@@ -7363,9 +7359,9 @@ async function mix(shouldMix, what, hexMirrors) {
   if (shouldMix === 'true') {
     const cmd = 'mix'
     const args = [`local.${what}`, '--force']
-    console.log(`##[group]Running ${cmd} ${args}`)
+    core.startGroup(`Running ${cmd} ${args}`)
     await mixWithMirrors(cmd, args, hexMirrors)
-    console.log('##[endgroup]')
+    core.endGroup()
   }
 }
 
@@ -7374,11 +7370,11 @@ async function maybeInstallGleam(gleamSpec) {
 
   if (gleamSpec) {
     const gleamVersion = await getGleamVersion(gleamSpec)
-    console.log(`##[group]Installing Gleam ${gleamVersion}`)
+    core.startGroup(`Installing Gleam ${gleamVersion}`)
     await installer.installGleam(gleamVersion)
     core.setOutput('gleam-version', gleamVersion)
     core.addPath(`${process.env.RUNNER_TEMP}/.setup-beam/gleam/bin`)
-    console.log('##[endgroup]')
+    core.endGroup()
 
     installed = true
   }
@@ -7396,11 +7392,11 @@ async function maybeInstallRebar3(rebar3Spec) {
     } else {
       rebar3Version = await getRebar3Version(rebar3Spec)
     }
-    console.log(`##[group]Installing rebar3 ${rebar3Version}`)
+    core.startGroup(`Installing rebar3 ${rebar3Version}`)
     await installer.installRebar3(rebar3Version)
     core.setOutput('rebar3-version', rebar3Version)
     core.addPath(`${process.env.RUNNER_TEMP}/.setup-beam/rebar3/bin`)
-    console.log('##[endgroup]')
+    core.endGroup()
 
     installed = true
   }
@@ -7493,16 +7489,16 @@ async function getRebar3Version(r3Spec) {
 
 async function getOTPVersions(osVersion, hexMirrors) {
   let otpVersionsListings
+  let originListing
   if (process.platform === 'linux') {
-    otpVersionsListings = await getWithMirrors(
-      `/builds/otp/${osVersion}/builds.txt`,
-      hexMirrors,
-    )
+    originListing = `/builds/otp/${osVersion}/builds.txt`
+    otpVersionsListings = await getWithMirrors(originListing, hexMirrors)
   } else if (process.platform === 'win32') {
-    const originListing =
+    originListing =
       'https://api.github.com/repos/erlang/otp/releases?per_page=100'
     otpVersionsListings = await get(originListing, [1, 2, 3])
   }
+  debugLog(`OTP versions listings from ${originListing}`, otpVersionsListings)
 
   const otpVersions = new Map()
 
@@ -7519,7 +7515,7 @@ async function getOTPVersions(osVersion, hexMirrors) {
       })
   } else if (process.platform === 'win32') {
     otpVersionsListings.forEach((otpVersionsListing) => {
-      jsonParse(otpVersionsListing)
+      jsonParseAsList(otpVersionsListing)
         .map((x) => x.assets)
         .flat()
         .filter((x) => x.name.match(/^otp_win64_.*.exe$/))
@@ -7566,7 +7562,7 @@ async function getGleamVersions() {
   )
   const gleamVersionsListing = []
   resultJSONs.forEach((resultJSON) => {
-    jsonParse(resultJSON)
+    jsonParseAsList(resultJSON)
       .map((x) => x.tag_name)
       .sort()
       .forEach((v) => gleamVersionsListing.push(v))
@@ -7581,7 +7577,7 @@ async function getRebar3Versions() {
   )
   const rebar3VersionsListing = []
   resultJSONs.forEach((resultJSON) => {
-    jsonParse(resultJSON)
+    jsonParseAsList(resultJSON)
       .map((x) => x.tag_name)
       .sort()
       .forEach((v) => rebar3VersionsListing.push(v))
@@ -7772,7 +7768,7 @@ function parseVersionFile(versionFilePath0) {
       `The specified version file, ${versionFilePath0}, does not exist`,
     )
   }
-  console.log(`##[group]Parsing version file at ${versionFilePath0}`)
+  core.startGroup(`Parsing version file at ${versionFilePath0}`)
   const appVersions = new Map()
   const versions = fs.readFileSync(versionFilePath, 'utf8')
   // For the time being we parse .tool-versions
@@ -7784,31 +7780,43 @@ function parseVersionFile(versionFilePath0) {
       const app = appVersion[1]
       if (['erlang', 'elixir', 'gleam', 'rebar'].includes(app)) {
         const [, , version] = appVersion
-        console.log(`Consuming ${app} at version ${version}`)
+        core.info(`Consuming ${app} at version ${version}`)
         appVersions.set(app, version)
       }
     }
   })
   if (!appVersions.size) {
-    console.log('There was apparently nothing to consume')
+    core.info('There was apparently nothing to consume')
   } else {
-    console.log('... done!')
+    core.info('... done!')
   }
-  console.log('##[endgroup]')
+  core.endGroup()
 
   return appVersions
 }
 
-function jsonParse(maybeJson) {
+function jsonParseAsList(maybeJson) {
   try {
-    return JSON.parse(maybeJson)
+    const obj = JSON.parse(maybeJson)
+    if (!Array.isArray(obj)) {
+      throw new Error('expected a list!')
+    }
+    return obj
   } catch (exc) {
     throw new Error(
-      `Got an exception when trying to parse non-JSON ${maybeJson}: ${exc}`,
+      `Got an exception when trying to parse non-JSON list ${maybeJson}: ${exc}`,
     )
   }
 }
 
+function debugLog(groupName, message) {
+  if (process.env.RUNNER_DEBUG) {
+    core.startGroup(`Debugging for ${groupName}`)
+    core.debug(message)
+    core.endGroup()
+  }
+}
+
 module.exports = {
   getOTPVersion,
   getElixirVersion,
diff --git a/matchers/elixir-matchers.json b/matchers/elixir-matchers.json
new file mode 100644
index 0000000..df01df6
--- /dev/null
+++ b/matchers/elixir-matchers.json
@@ -0,0 +1,62 @@
+{
+  "problemMatcher": [
+    {
+      "owner": "elixir-mixCompileError",
+      "severity": "error",
+      "pattern": [
+        {
+          "regexp": "^\\*\\* \\((\\w+)\\) (.*):(\\d+): (.*)$",
+          "file": 2,
+          "line": 3,
+          "message": 0
+        }
+      ]
+    },
+    {
+      "owner": "elixir-mixCompileWarning",
+      "severity": "warning",
+      "pattern": [
+        {
+          "regexp": "^warning: (.*)$",
+          "message": 1
+        },
+        {
+          "regexp": "^  (.*):(\\d+).*$",
+          "file": 1,
+          "line": 2
+        }
+      ]
+    },
+    {
+      "owner": "elixir-mixTestFailure",
+      "severity": "error",
+      "pattern": [
+        {
+          "regexp": "^\\s*\\d+\\) (.*)$",
+          "message": 1
+        },
+        {
+          "regexp": "^\\s*(.*):(\\d+)$",
+          "file": 1,
+          "line": 2
+        }
+      ]
+    },
+    {
+      "owner": "elixir-credoOutputDefault",
+      "severity": "warning",
+      "pattern": [
+        {
+          "regexp": "^\u2503\\s\\[\\w\\]\\s[\u2191|\u2197|\u2192|\u2198|\u2193]\\s(.*)$",
+          "message": 1
+        },
+        {
+          "regexp": "^\u2503\\s{7}(.*):(\\d+):(\\d+)\\s.*$",
+          "file": 1,
+          "line": 2,
+          "column": 3
+        }
+      ]
+    }
+  ]
+}
diff --git a/package-lock.json b/package-lock.json
index 1de8078..7f75f52 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -9,7 +9,7 @@
       "dependencies": {
         "@actions/core": "1.10.0",
         "@actions/exec": "1.1.1",
-        "@actions/http-client": "^2.1.0",
+        "@actions/http-client": "2.1.0",
         "semver": "7.3.8"
       },
       "devDependencies": {
diff --git a/package.json b/package.json
index 52967c3..a7d1a0b 100644
--- a/package.json
+++ b/package.json
@@ -4,12 +4,12 @@
   "private": true,
   "scripts": {
     "build": "ncc build src/setup-beam.js --no-cache",
-    "format": "prettier src/**/*.js --write && prettier __tests__/**/*.js --write",
-    "jslint": "eslint src/**/*.js && eslint __tests__/**/*.js",
+    "format": "prettier src/**/*.js --write && prettier test/**/*.js --write",
+    "jslint": "eslint src/**/*.js && eslint test/**/*.js",
     "licenses": "yarn licenses generate-disclaimer > 3RD_PARTY_LICENSES",
     "markdownlint": "markdownlint *.md",
     "shellcheck": "shellcheck src/install-*.sh .github/workflows/*.sh",
-    "test": "node __tests__/setup-beam.test.js && node ./__tests__/problem-matchers.test.js",
+    "test": "node test/setup-beam.test.js && node ./test/problem-matchers.test.js",
     "yamllint": "yamllint .github/workflows/**.yml && yamllint .*.yml && yamllint *.yml",
     "build-dist": "npm install && npm run build && npm run format && npm run markdownlint && npm run shellcheck && npm run yamllint && npm run jslint"
   },
diff --git a/src/setup-beam.js b/src/setup-beam.js
index 9e73f1a..75f08e9 100644
--- a/src/setup-beam.js
+++ b/src/setup-beam.js
@@ -58,13 +58,11 @@ async function main() {
 
 async function installOTP(otpSpec, osVersion, hexMirrors) {
   const otpVersion = await getOTPVersion(otpSpec, osVersion, hexMirrors)
-  console.log(
-    `##[group]Installing Erlang/OTP ${otpVersion} - built on ${osVersion}`,
-  )
+  core.startGroup(`Installing Erlang/OTP ${otpVersion} - built on ${osVersion}`)
   await installer.installOTP(osVersion, otpVersion, hexMirrors)
   core.setOutput('otp-version', otpVersion)
   core.addPath(`${process.env.RUNNER_TEMP}/.setup-beam/otp/bin`)
-  console.log('##[endgroup]')
+  core.endGroup()
 
   return otpVersion
 }
@@ -78,19 +76,22 @@ async function maybeInstallElixir(elixirSpec, otpSpec, hexMirrors) {
       otpSpec,
       hexMirrors,
     )
-    console.log(`##[group]Installing Elixir ${elixirVersion}`)
+    core.startGroup(`Installing Elixir ${elixirVersion}`)
     await installer.installElixir(elixirVersion, hexMirrors)
     core.setOutput('elixir-version', elixirVersion)
     const disableProblemMatchers = getInput('disable_problem_matchers', false)
     if (disableProblemMatchers === 'false') {
-      const matchersPath = path.join(__dirname, '..', '.github')
-      console.log(
-        `##[add-matcher]${path.join(matchersPath, 'elixir-matchers.json')}`,
+      const elixirMatchers = path.join(
+        __dirname,
+        '..',
+        'matchers',
+        'elixir-matchers.json',
       )
+      core.info(`##[add-matcher]${elixirMatchers}`)
     }
     core.addPath(`${os.homedir()}/.mix/escripts`)
     core.addPath(`${process.env.RUNNER_TEMP}/.setup-beam/elixir/bin`)
-    console.log('##[endgroup]')
+    core.endGroup()
 
     installed = true
   }
@@ -118,9 +119,9 @@ async function mix(shouldMix, what, hexMirrors) {
   if (shouldMix === 'true') {
     const cmd = 'mix'
     const args = [`local.${what}`, '--force']
-    console.log(`##[group]Running ${cmd} ${args}`)
+    core.startGroup(`Running ${cmd} ${args}`)
     await mixWithMirrors(cmd, args, hexMirrors)
-    console.log('##[endgroup]')
+    core.endGroup()
   }
 }
 
@@ -129,11 +130,11 @@ async function maybeInstallGleam(gleamSpec) {
 
   if (gleamSpec) {
     const gleamVersion = await getGleamVersion(gleamSpec)
-    console.log(`##[group]Installing Gleam ${gleamVersion}`)
+    core.startGroup(`Installing Gleam ${gleamVersion}`)
     await installer.installGleam(gleamVersion)
     core.setOutput('gleam-version', gleamVersion)
     core.addPath(`${process.env.RUNNER_TEMP}/.setup-beam/gleam/bin`)
-    console.log('##[endgroup]')
+    core.endGroup()
 
     installed = true
   }
@@ -151,11 +152,11 @@ async function maybeInstallRebar3(rebar3Spec) {
     } else {
       rebar3Version = await getRebar3Version(rebar3Spec)
     }
-    console.log(`##[group]Installing rebar3 ${rebar3Version}`)
+    core.startGroup(`Installing rebar3 ${rebar3Version}`)
     await installer.installRebar3(rebar3Version)
     core.setOutput('rebar3-version', rebar3Version)
     core.addPath(`${process.env.RUNNER_TEMP}/.setup-beam/rebar3/bin`)
-    console.log('##[endgroup]')
+    core.endGroup()
 
     installed = true
   }
@@ -248,16 +249,16 @@ async function getRebar3Version(r3Spec) {
 
 async function getOTPVersions(osVersion, hexMirrors) {
   let otpVersionsListings
+  let originListing
   if (process.platform === 'linux') {
-    otpVersionsListings = await getWithMirrors(
-      `/builds/otp/${osVersion}/builds.txt`,
-      hexMirrors,
-    )
+    originListing = `/builds/otp/${osVersion}/builds.txt`
+    otpVersionsListings = await getWithMirrors(originListing, hexMirrors)
   } else if (process.platform === 'win32') {
-    const originListing =
+    originListing =
       'https://api.github.com/repos/erlang/otp/releases?per_page=100'
     otpVersionsListings = await get(originListing, [1, 2, 3])
   }
+  debugLog(`OTP versions listings from ${originListing}`, otpVersionsListings)
 
   const otpVersions = new Map()
 
@@ -274,7 +275,7 @@ async function getOTPVersions(osVersion, hexMirrors) {
       })
   } else if (process.platform === 'win32') {
     otpVersionsListings.forEach((otpVersionsListing) => {
-      jsonParse(otpVersionsListing)
+      jsonParseAsList(otpVersionsListing)
         .map((x) => x.assets)
         .flat()
         .filter((x) => x.name.match(/^otp_win64_.*.exe$/))
@@ -321,7 +322,7 @@ async function getGleamVersions() {
   )
   const gleamVersionsListing = []
   resultJSONs.forEach((resultJSON) => {
-    jsonParse(resultJSON)
+    jsonParseAsList(resultJSON)
       .map((x) => x.tag_name)
       .sort()
       .forEach((v) => gleamVersionsListing.push(v))
@@ -336,7 +337,7 @@ async function getRebar3Versions() {
   )
   const rebar3VersionsListing = []
   resultJSONs.forEach((resultJSON) => {
-    jsonParse(resultJSON)
+    jsonParseAsList(resultJSON)
       .map((x) => x.tag_name)
       .sort()
       .forEach((v) => rebar3VersionsListing.push(v))
@@ -527,7 +528,7 @@ function parseVersionFile(versionFilePath0) {
       `The specified version file, ${versionFilePath0}, does not exist`,
     )
   }
-  console.log(`##[group]Parsing version file at ${versionFilePath0}`)
+  core.startGroup(`Parsing version file at ${versionFilePath0}`)
   const appVersions = new Map()
   const versions = fs.readFileSync(versionFilePath, 'utf8')
   // For the time being we parse .tool-versions
@@ -539,31 +540,43 @@ function parseVersionFile(versionFilePath0) {
       const app = appVersion[1]
       if (['erlang', 'elixir', 'gleam', 'rebar'].includes(app)) {
         const [, , version] = appVersion
-        console.log(`Consuming ${app} at version ${version}`)
+        core.info(`Consuming ${app} at version ${version}`)
         appVersions.set(app, version)
       }
     }
   })
   if (!appVersions.size) {
-    console.log('There was apparently nothing to consume')
+    core.info('There was apparently nothing to consume')
   } else {
-    console.log('... done!')
+    core.info('... done!')
   }
-  console.log('##[endgroup]')
+  core.endGroup()
 
   return appVersions
 }
 
-function jsonParse(maybeJson) {
+function jsonParseAsList(maybeJson) {
   try {
-    return JSON.parse(maybeJson)
+    const obj = JSON.parse(maybeJson)
+    if (!Array.isArray(obj)) {
+      throw new Error('expected a list!')
+    }
+    return obj
   } catch (exc) {
     throw new Error(
-      `Got an exception when trying to parse non-JSON ${maybeJson}: ${exc}`,
+      `Got an exception when trying to parse non-JSON list ${maybeJson}: ${exc}`,
     )
   }
 }
 
+function debugLog(groupName, message) {
+  if (process.env.RUNNER_DEBUG) {
+    core.startGroup(`Debugging for ${groupName}`)
+    core.debug(message)
+    core.endGroup()
+  }
+}
+
 module.exports = {
   getOTPVersion,
   getElixirVersion,
diff --git a/__tests__/problem-matchers.test.js b/test/problem-matchers.test.js
similarity index 95%
rename from __tests__/problem-matchers.test.js
rename to test/problem-matchers.test.js
index e8d0d78..5e21011 100644
--- a/__tests__/problem-matchers.test.js
+++ b/test/problem-matchers.test.js
@@ -1,5 +1,6 @@
 const assert = require('assert')
-const { problemMatcher } = require('../.github/elixir-matchers.json')
+const core = require('@actions/core')
+const { problemMatcher } = require('../matchers/elixir-matchers.json')
 
 async function all() {
   await testElixirMixCompileError()
@@ -76,6 +77,6 @@ async function testElixirCredoOutputDefault() {
 all()
   .then(() => process.exit(0))
   .catch((err) => {
-    console.error(err)
+    core.error(err)
     process.exit(1)
   })
diff --git a/test-projects/elixir_mix/.formatter.exs b/test/projects/elixir_mix/.formatter.exs
similarity index 100%
rename from test-projects/elixir_mix/.formatter.exs
rename to test/projects/elixir_mix/.formatter.exs
diff --git a/test-projects/elixir_mix/.gitignore b/test/projects/elixir_mix/.gitignore
similarity index 100%
rename from test-projects/elixir_mix/.gitignore
rename to test/projects/elixir_mix/.gitignore
diff --git a/test-projects/elixir_mix/README.md b/test/projects/elixir_mix/README.md
similarity index 100%
rename from test-projects/elixir_mix/README.md
rename to test/projects/elixir_mix/README.md
diff --git a/test-projects/elixir_mix/lib/test.ex b/test/projects/elixir_mix/lib/test.ex
similarity index 100%
rename from test-projects/elixir_mix/lib/test.ex
rename to test/projects/elixir_mix/lib/test.ex
diff --git a/test-projects/elixir_mix/mix.exs b/test/projects/elixir_mix/mix.exs
similarity index 100%
rename from test-projects/elixir_mix/mix.exs
rename to test/projects/elixir_mix/mix.exs
diff --git a/test-projects/elixir_mix/mix.lock b/test/projects/elixir_mix/mix.lock
similarity index 100%
rename from test-projects/elixir_mix/mix.lock
rename to test/projects/elixir_mix/mix.lock
diff --git a/test-projects/elixir_mix/test/test_helper.exs b/test/projects/elixir_mix/test/test_helper.exs
similarity index 100%
rename from test-projects/elixir_mix/test/test_helper.exs
rename to test/projects/elixir_mix/test/test_helper.exs
diff --git a/test-projects/elixir_mix/test/test_test.exs b/test/projects/elixir_mix/test/test_test.exs
similarity index 100%
rename from test-projects/elixir_mix/test/test_test.exs
rename to test/projects/elixir_mix/test/test_test.exs
diff --git a/test-projects/erlang_rebar3/.gitignore b/test/projects/erlang_rebar3/.gitignore
similarity index 100%
rename from test-projects/erlang_rebar3/.gitignore
rename to test/projects/erlang_rebar3/.gitignore
diff --git a/test-projects/erlang_rebar3/LICENSE b/test/projects/erlang_rebar3/LICENSE
similarity index 100%
rename from test-projects/erlang_rebar3/LICENSE
rename to test/projects/erlang_rebar3/LICENSE
diff --git a/test-projects/erlang_rebar3/README.md b/test/projects/erlang_rebar3/README.md
similarity index 100%
rename from test-projects/erlang_rebar3/README.md
rename to test/projects/erlang_rebar3/README.md
diff --git a/test-projects/erlang_rebar3/rebar.config b/test/projects/erlang_rebar3/rebar.config
similarity index 100%
rename from test-projects/erlang_rebar3/rebar.config
rename to test/projects/erlang_rebar3/rebar.config
diff --git a/test-projects/erlang_rebar3/rebar.lock b/test/projects/erlang_rebar3/rebar.lock
similarity index 100%
rename from test-projects/erlang_rebar3/rebar.lock
rename to test/projects/erlang_rebar3/rebar.lock
diff --git a/test-projects/erlang_rebar3/src/mylib.app.src b/test/projects/erlang_rebar3/src/mylib.app.src
similarity index 100%
rename from test-projects/erlang_rebar3/src/mylib.app.src
rename to test/projects/erlang_rebar3/src/mylib.app.src
diff --git a/test-projects/erlang_rebar3/src/mylib.erl b/test/projects/erlang_rebar3/src/mylib.erl
similarity index 100%
rename from test-projects/erlang_rebar3/src/mylib.erl
rename to test/projects/erlang_rebar3/src/mylib.erl
diff --git a/test-projects/erlang_rebar3/test/mylib_SUITE.erl b/test/projects/erlang_rebar3/test/mylib_SUITE.erl
similarity index 100%
rename from test-projects/erlang_rebar3/test/mylib_SUITE.erl
rename to test/projects/erlang_rebar3/test/mylib_SUITE.erl
diff --git a/test-projects/gleam_gleam/.github/workflows/test.yml b/test/projects/gleam_gleam/.github/workflows/test.yml
similarity index 100%
rename from test-projects/gleam_gleam/.github/workflows/test.yml
rename to test/projects/gleam_gleam/.github/workflows/test.yml
diff --git a/test-projects/gleam_gleam/.gitignore b/test/projects/gleam_gleam/.gitignore
similarity index 100%
rename from test-projects/gleam_gleam/.gitignore
rename to test/projects/gleam_gleam/.gitignore
diff --git a/test-projects/gleam_gleam/README.md b/test/projects/gleam_gleam/README.md
similarity index 100%
rename from test-projects/gleam_gleam/README.md
rename to test/projects/gleam_gleam/README.md
diff --git a/test-projects/gleam_gleam/gleam.toml b/test/projects/gleam_gleam/gleam.toml
similarity index 100%
rename from test-projects/gleam_gleam/gleam.toml
rename to test/projects/gleam_gleam/gleam.toml
diff --git a/test-projects/gleam_gleam/manifest.toml b/test/projects/gleam_gleam/manifest.toml
similarity index 100%
rename from test-projects/gleam_gleam/manifest.toml
rename to test/projects/gleam_gleam/manifest.toml
diff --git a/test-projects/gleam_gleam/src/gleam_gleam.gleam b/test/projects/gleam_gleam/src/gleam_gleam.gleam
similarity index 100%
rename from test-projects/gleam_gleam/src/gleam_gleam.gleam
rename to test/projects/gleam_gleam/src/gleam_gleam.gleam
diff --git a/test-projects/gleam_gleam/test/gleam_gleam_test.gleam b/test/projects/gleam_gleam/test/gleam_gleam_test.gleam
similarity index 100%
rename from test-projects/gleam_gleam/test/gleam_gleam_test.gleam
rename to test/projects/gleam_gleam/test/gleam_gleam_test.gleam
diff --git a/test-projects/rust_rebar3_cmd/.gitignore b/test/projects/rust_rebar3_cmd/.gitignore
similarity index 100%
rename from test-projects/rust_rebar3_cmd/.gitignore
rename to test/projects/rust_rebar3_cmd/.gitignore
diff --git a/test-projects/rust_rebar3_cmd/Cargo.lock b/test/projects/rust_rebar3_cmd/Cargo.lock
similarity index 100%
rename from test-projects/rust_rebar3_cmd/Cargo.lock
rename to test/projects/rust_rebar3_cmd/Cargo.lock
diff --git a/test-projects/rust_rebar3_cmd/Cargo.toml b/test/projects/rust_rebar3_cmd/Cargo.toml
similarity index 100%
rename from test-projects/rust_rebar3_cmd/Cargo.toml
rename to test/projects/rust_rebar3_cmd/Cargo.toml
diff --git a/test-projects/rust_rebar3_cmd/src/main.rs b/test/projects/rust_rebar3_cmd/src/main.rs
similarity index 100%
rename from test-projects/rust_rebar3_cmd/src/main.rs
rename to test/projects/rust_rebar3_cmd/src/main.rs
diff --git a/__tests__/setup-beam.test.js b/test/setup-beam.test.js
similarity index 91%
rename from __tests__/setup-beam.test.js
rename to test/setup-beam.test.js
index 2496823..d05c8b7 100644
--- a/__tests__/setup-beam.test.js
+++ b/test/setup-beam.test.js
@@ -4,9 +4,11 @@ simulateInput('rebar3-version', '3.20')
 simulateInput('install-rebar', 'true')
 simulateInput('install-hex', 'true')
 simulateInput('github-token', process.env.GITHUB_TOKEN)
+simulateInput('hexpm-mirrors', ['https://builds.hex.pm'])
 
 const assert = require('assert')
 const fs = require('fs')
+const core = require('@actions/core')
 const setupBeam = require('../src/setup-beam')
 const installer = require('../src/installer')
 
@@ -174,6 +176,7 @@ async function testElixirVersions() {
   let expected
   let spec
   let otpVersion
+  let before
   const hexMirrors = ['https://repo.hex.pm']
 
   spec = '1.1.x'
@@ -194,37 +197,37 @@ async function testElixirVersions() {
   got = await setupBeam.getElixirVersion(spec, otpVersion, hexMirrors)
   assert.deepStrictEqual(got, expected)
 
-  simulateInput('version-type', 'strict')
+  before = simulateInput('version-type', 'strict')
   spec = '1.14.0'
   otpVersion = 'master'
   expected = 'v1.14.0'
   got = await setupBeam.getElixirVersion(spec, otpVersion, hexMirrors)
   assert.deepStrictEqual(got, expected)
-  simulateInput('version-type', 'loose')
+  simulateInput('version-type', before)
 
-  simulateInput('version-type', 'strict')
+  before = simulateInput('version-type', 'strict')
   spec = 'v1.11.0-rc.0'
   otpVersion = 'OTP-23'
   expected = 'v1.11.0-rc.0-otp-23'
   got = await setupBeam.getElixirVersion(spec, otpVersion, hexMirrors)
   assert.deepStrictEqual(got, expected)
-  simulateInput('version-type', 'loose')
+  simulateInput('version-type', before)
 
-  simulateInput('version-type', 'strict')
+  before = simulateInput('version-type', 'strict')
   spec = 'v1.11.0'
   otpVersion = '22.3.4.2'
   expected = 'v1.11.0-otp-22'
   got = await setupBeam.getElixirVersion(spec, otpVersion, hexMirrors)
   assert.deepStrictEqual(got, expected)
-  simulateInput('version-type', 'loose')
+  simulateInput('version-type', before)
 
-  simulateInput('version-type', 'strict')
+  before = simulateInput('version-type', 'strict')
   spec = 'main'
   otpVersion = '23.1'
   expected = 'main-otp-23'
   got = await setupBeam.getElixirVersion(spec, otpVersion, hexMirrors)
   assert.deepStrictEqual(got, expected)
-  simulateInput('version-type', 'loose')
+  simulateInput('version-type', before)
 }
 
 async function testGleamVersions() {
@@ -245,13 +248,13 @@ async function testGleamVersions() {
   got = await setupBeam.getGleamVersion(spec, otpVersion)
   assert.deepStrictEqual(got, expected)
 
-  simulateInput('version-type', 'strict')
+  const before = simulateInput('version-type', 'strict')
   spec = 'v0.14.0-rc2'
   otpVersion = 'OTP-22'
   expected = 'v0.14.0-rc2'
   got = await setupBeam.getGleamVersion(spec, otpVersion)
   assert.deepStrictEqual(got, expected)
-  simulateInput('version-type', 'loose')
+  simulateInput('version-type', before)
 }
 
 async function testRebar3Versions() {
@@ -279,6 +282,7 @@ async function testGetVersionFromSpec() {
   let got
   let expected
   let spec
+  let before
   const versions = [
     '3.2.30.5',
     '3.2.3.5',
@@ -320,19 +324,19 @@ async function testGetVersionFromSpec() {
   got = setupBeam.getVersionFromSpec(spec, versions)
   assert.deepStrictEqual(got, expected)
 
-  simulateInput('version-type', 'strict')
+  before = simulateInput('version-type', 'strict')
   spec = '1'
   expected = '1'
   got = setupBeam.getVersionFromSpec(spec, versions)
   assert.deepStrictEqual(got, expected)
-  simulateInput('version-type', 'loose')
+  simulateInput('version-type', before)
 
-  simulateInput('version-type', 'strict')
+  before = simulateInput('version-type', 'strict')
   spec = '1.0'
   expected = '1.0'
   got = setupBeam.getVersionFromSpec(spec, versions)
   assert.deepStrictEqual(got, expected)
-  simulateInput('version-type', 'loose')
+  simulateInput('version-type', before)
 
   spec = '2'
   expected = '2.10'
@@ -359,12 +363,12 @@ async function testGetVersionFromSpec() {
   got = setupBeam.getVersionFromSpec(spec, versions)
   assert.deepStrictEqual(got, expected)
 
-  simulateInput('version-type', 'strict')
+  before = simulateInput('version-type', 'strict')
   spec = '24.0-rc3'
   expected = '24.0-rc3'
   got = setupBeam.getVersionFromSpec(spec, versions)
   assert.deepStrictEqual(got, expected)
-  simulateInput('version-type', 'loose')
+  simulateInput('version-type', before)
 
   spec = '24.0-rc2'
   expected = '24.0-rc2'
@@ -391,24 +395,24 @@ async function testGetVersionFromSpec() {
   got = setupBeam.getVersionFromSpec(spec, versions)
   assert.deepStrictEqual(got, expected)
 
-  simulateInput('version-type', 'strict')
+  before = simulateInput('version-type', 'strict')
   spec = 'master'
   expected = 'master'
   got = setupBeam.getVersionFromSpec(spec, versions)
   assert.deepStrictEqual(got, expected)
-  simulateInput('version-type', 'loose')
+  simulateInput('version-type', before)
 
   spec = 'master'
   expected = 'master'
   got = setupBeam.getVersionFromSpec(spec, versions)
   assert.deepStrictEqual(got, expected)
 
-  simulateInput('version-type', 'strict')
+  before = simulateInput('version-type', 'strict')
   spec = '22.3.4.2'
   expected = '22.3.4.2'
   got = setupBeam.getVersionFromSpec(spec, versions)
   assert.deepStrictEqual(got, expected)
-  simulateInput('version-type', 'loose')
+  simulateInput('version-type', before)
 }
 
 async function testParseVersionFile() {
@@ -427,7 +431,7 @@ elixir ${elixir}  # comment, with space
  not-gleam 0.23 # not picked up
 gleam ${gleam} 
 rebar ${rebar3}`
-  const filename = '__tests__/.tool-versions'
+  const filename = 'test/.tool-versions'
   fs.writeFileSync(filename, toolVersions)
   process.env.GITHUB_WORKSPACE = ''
   const appVersions = setupBeam.parseVersionFile(filename)
@@ -454,13 +458,13 @@ rebar ${rebar3}`
 }
 
 function unsimulateInput(key) {
-  const before = process.env[input(key)]
-  simulateInput(key, '')
-  return before
+  return simulateInput(key, '')
 }
 
 function simulateInput(key, value) {
+  const before = process.env[input(key)]
   process.env[input(key)] = value
+  return before
 }
 
 function input(key) {
@@ -470,6 +474,6 @@ function input(key) {
 all()
   .then(() => process.exit(0))
   .catch((err) => {
-    console.error(err)
+    core.error(err)
     process.exit(1)
   })