diff --git a/poetry.lock b/poetry.lock
index 81bff637e44..7a480f091a6 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -687,7 +687,7 @@ category = "main"
 description = "Core utilities for Poetry"
 name = "poetry-core"
 optional = false
-python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*"
+python-versions = "~2.7 || ^3.5"
 version = "1.0.0a9"
 
 [package.dependencies]
@@ -697,6 +697,10 @@ importlib-metadata = {version = ">=1.7.0,<2.0.0", markers = "python_version >= \
 pathlib2 = {version = ">=2.3.5,<3.0.0", markers = "python_version >= \"2.7\" and python_version < \"2.8\""}
 typing = {version = ">=3.7.4.1,<4.0.0.0", markers = "python_version >= \"2.7\" and python_version < \"2.8\""}
 
+[package.source]
+reference = "0658ad01a805310d1fc96891dae3e9b7a420727c"
+type = "git"
+url = "https://github.com/abn/poetry-core.git"
 [[package]]
 category = "dev"
 description = "A framework for managing and maintaining multi-language pre-commit hooks."
@@ -1160,7 +1164,7 @@ docs = ["sphinx", "jaraco.packaging (>=3.2)", "rst.linker (>=1.9)"]
 testing = ["pathlib2", "unittest2", "jaraco.itertools", "func-timeout"]
 
 [metadata]
-content-hash = "20c1d02c76ead833a0b43da34477554bdb262f20fd1b7a8b530a5bf551cd9d4a"
+content-hash = "cc8c9da62ac7663cb2192ebcf38a9afdc4c98cc50cfa49c398d6f45eae035e77"
 lock-version = "1.1"
 python-versions = "~2.7 || ^3.5"
 
@@ -1437,6 +1441,11 @@ markupsafe = [
     {file = "MarkupSafe-1.1.1-cp37-cp37m-manylinux1_x86_64.whl", hash = "sha256:ba59edeaa2fc6114428f1637ffff42da1e311e29382d81b339c1817d37ec93c6"},
     {file = "MarkupSafe-1.1.1-cp37-cp37m-win32.whl", hash = "sha256:b00c1de48212e4cc9603895652c5c410df699856a2853135b3967591e4beebc2"},
     {file = "MarkupSafe-1.1.1-cp37-cp37m-win_amd64.whl", hash = "sha256:9bf40443012702a1d2070043cb6291650a0841ece432556f784f004937f0f32c"},
+    {file = "MarkupSafe-1.1.1-cp38-cp38-macosx_10_9_x86_64.whl", hash = "sha256:6788b695d50a51edb699cb55e35487e430fa21f1ed838122d722e0ff0ac5ba15"},
+    {file = "MarkupSafe-1.1.1-cp38-cp38-manylinux1_i686.whl", hash = "sha256:cdb132fc825c38e1aeec2c8aa9338310d29d337bebbd7baa06889d09a60a1fa2"},
+    {file = "MarkupSafe-1.1.1-cp38-cp38-manylinux1_x86_64.whl", hash = "sha256:13d3144e1e340870b25e7b10b98d779608c02016d5184cfb9927a9f10c689f42"},
+    {file = "MarkupSafe-1.1.1-cp38-cp38-win32.whl", hash = "sha256:596510de112c685489095da617b5bcbbac7dd6384aeebeda4df6025d0256a81b"},
+    {file = "MarkupSafe-1.1.1-cp38-cp38-win_amd64.whl", hash = "sha256:e8313f01ba26fbbe36c7be1966a7b7424942f670f38e666995b88d012765b9be"},
     {file = "MarkupSafe-1.1.1.tar.gz", hash = "sha256:29872e92839765e546828bb7754a68c418d927cd064fd4708fab9fe9c8bb116b"},
 ]
 mkdocs = [
@@ -1511,10 +1520,7 @@ pluggy = [
     {file = "pluggy-0.13.1-py2.py3-none-any.whl", hash = "sha256:966c145cd83c96502c3c3868f50408687b38434af77734af1e9ca461a4081d2d"},
     {file = "pluggy-0.13.1.tar.gz", hash = "sha256:15b2acde666561e1298d71b523007ed7364de07029219b604cf808bfa1c765b0"},
 ]
-poetry-core = [
-    {file = "poetry-core-1.0.0a9.tar.gz", hash = "sha256:f08e9829fd06609ca5615faa91739b589eb71e025a6aaf7ddffb698676eb7c8c"},
-    {file = "poetry_core-1.0.0a9-py2.py3-none-any.whl", hash = "sha256:79a63629ae44533ba9aa828e0eff0002c61b3af5fc9bec212e006cc643f4eb19"},
-]
+poetry-core = []
 pre-commit = [
     {file = "pre_commit-2.6.0-py2.py3-none-any.whl", hash = "sha256:e8b1315c585052e729ab7e99dcca5698266bedce9067d21dc909c23e3ceed626"},
     {file = "pre_commit-2.6.0.tar.gz", hash = "sha256:1657663fdd63a321a4a739915d7d03baedd555b25054449090f97bb0cb30a915"},
@@ -1603,7 +1609,6 @@ regex = [
     {file = "regex-2020.7.14-cp38-cp38-manylinux1_i686.whl", hash = "sha256:5ea81ea3dbd6767873c611687141ec7b06ed8bab43f68fad5b7be184a920dc99"},
     {file = "regex-2020.7.14-cp38-cp38-manylinux1_x86_64.whl", hash = "sha256:bbb332d45b32df41200380fff14712cb6093b61bd142272a10b16778c418e98e"},
     {file = "regex-2020.7.14-cp38-cp38-manylinux2010_i686.whl", hash = "sha256:c11d6033115dc4887c456565303f540c44197f4fc1a2bfb192224a301534888e"},
-    {file = "regex-2020.7.14-cp38-cp38-manylinux2010_x86_64.whl", hash = "sha256:75aaa27aa521a182824d89e5ab0a1d16ca207318a6b65042b046053cfc8ed07a"},
     {file = "regex-2020.7.14-cp38-cp38-win32.whl", hash = "sha256:d6cff2276e502b86a25fd10c2a96973fdb45c7a977dca2138d661417f3728341"},
     {file = "regex-2020.7.14-cp38-cp38-win_amd64.whl", hash = "sha256:7a2dd66d2d4df34fa82c9dc85657c5e019b87932019947faece7983f2089a840"},
     {file = "regex-2020.7.14.tar.gz", hash = "sha256:3a3af27a8d23143c49a3420efe5b3f8cf1a48c6fc8bc6856b03f638abc1833bb"},
diff --git a/poetry/console/commands/build.py b/poetry/console/commands/build.py
index 118fb210c53..073044698a9 100644
--- a/poetry/console/commands/build.py
+++ b/poetry/console/commands/build.py
@@ -1,9 +1,9 @@
 from cleo import option
 
-from .env_command import EnvCommand
+from poetry.console.commands.installer_command import InstallerCommand
 
 
-class BuildCommand(EnvCommand):
+class BuildCommand(InstallerCommand):
 
     name = "build"
     description = "Builds a package, as a tarball and a wheel by default."
@@ -33,4 +33,11 @@ def handle(self):
         )
 
         builder = Builder(self.poetry)
-        builder.build(fmt)
+
+        executable = None
+        if self.poetry.package.build_requires:
+            # ensure build requirements are available if specified
+            self.installer.categories({"build"}).run()
+            executable = self.installer.env.python
+
+        builder.build(fmt, executable=executable)
diff --git a/poetry/installation/base_installer.py b/poetry/installation/base_installer.py
index 1e068d076cd..de8b0086d9a 100644
--- a/poetry/installation/base_installer.py
+++ b/poetry/installation/base_installer.py
@@ -1,4 +1,8 @@
 class BaseInstaller:
+    @property
+    def env(self):
+        return getattr(self, "_env", None)
+
     def install(self, package):
         raise NotImplementedError
 
diff --git a/poetry/installation/installer.py b/poetry/installation/installer.py
index f0c9a62d65d..36878da225a 100644
--- a/poetry/installation/installer.py
+++ b/poetry/installation/installer.py
@@ -1,3 +1,4 @@
+from typing import Iterable
 from typing import List
 from typing import Optional
 from typing import Union
@@ -11,6 +12,7 @@
 from poetry.repositories import Pool
 from poetry.repositories import Repository
 from poetry.repositories.installed_repository import InstalledRepository
+from poetry.utils.env import Env
 from poetry.utils.extras import get_extra_package_names
 from poetry.utils.helpers import canonicalize_name
 
@@ -47,10 +49,12 @@ def __init__(
         self._verbose = False
         self._write_lock = True
         self._dev_mode = True
+        self._build_mode = True
         self._execute_operations = True
         self._lock = False
 
         self._whitelist = []
+        self._categories = set()
 
         self._extras = []
 
@@ -66,6 +70,10 @@ def __init__(
 
         self._installed_repository = installed
 
+    @property
+    def env(self):  # type: () -> Env
+        return self._env
+
     @property
     def executor(self):
         return self._executor
@@ -132,6 +140,14 @@ def dev_mode(self, dev_mode=True):  # type: (bool) -> Installer
     def is_dev_mode(self):  # type: () -> bool
         return self._dev_mode
 
+    def build_mode(self, build_mode=True):  # type: (bool) -> Installer
+        self._build_mode = build_mode
+
+        return self
+
+    def is_build_mode(self):  # type: () -> bool
+        return self._build_mode or self._dev_mode
+
     def update(self, update=True):  # type: (bool) -> Installer
         self._update = update
 
@@ -163,6 +179,13 @@ def whitelist(self, packages):  # type: (dict) -> Installer
 
         return self
 
+    def categories(
+        self, categories=None
+    ):  # type: (Optional[Iterable[str]]) -> Installer
+        self._categories = {category for category in categories or []}
+
+        return self
+
     def extras(self, extras):  # type: (list) -> Installer
         self._extras = extras
 
@@ -241,6 +264,10 @@ def _do_install(self, local_repo):
             root = root.clone()
             del root.dev_requires[:]
 
+        if not self.is_build_mode():
+            root = root.clone()
+            del root.build_requires[:]
+
         if self._io.is_verbose():
             self._io.write_line("")
             self._io.write_line(
@@ -455,6 +482,8 @@ def _get_operations_from_lock(
                     is_installed = True
                     if locked.category == "dev" and not self.is_dev_mode():
                         ops.append(Uninstall(locked))
+                    elif locked.category == "build" and not self.is_build_mode():
+                        ops.append(Uninstall(locked))
                     elif locked.optional and locked.name not in extra_packages:
                         # Installed but optional and not requested in extras
                         ops.append(Uninstall(locked))
@@ -506,11 +535,19 @@ def _filter_operations(
                 if package.name not in extra_packages:
                     op.skip("Not required")
 
+            if self._categories and package.category not in self._categories:
+                op.skip("Category ({}) not enabled".format(package.category))
+
             # If the package is a dev package and dev packages
             # are not requested, we skip it
             if package.category == "dev" and not self.is_dev_mode():
                 op.skip("Dev dependencies not requested")
 
+            # If the package is a build package and build packages
+            # are not requested, we skip it
+            if package.category == "build" and not self.is_build_mode():
+                op.skip("Build dependencies not requested")
+
     def _get_extra_packages(self, repo):  # type: (Repository) -> List[str]
         """
         Returns all package names required by extras.
diff --git a/poetry/puzzle/solver.py b/poetry/puzzle/solver.py
index 386d8f95a7f..5a82b47ab62 100644
--- a/poetry/puzzle/solver.py
+++ b/poetry/puzzle/solver.py
@@ -338,6 +338,8 @@ def _get_tags_for_package(self, package, graph, depth=0):
 
         if "main" in categories:
             category = "main"
+        elif "build" in categories:
+            category = "build"
         else:
             category = "dev"
 
diff --git a/pyproject.toml b/pyproject.toml
index 5ef380e92e1..33ff82b9a1a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -24,7 +24,7 @@ classifiers = [
 [tool.poetry.dependencies]
 python = "~2.7 || ^3.5"
 
-poetry-core = "^1.0.0a9"
+poetry-core = { git = "https://github.com/abn/poetry-core.git", branch = "support-build-system-requires"}
 cleo = "^0.8.1"
 clikit = "^0.6.2"
 crashtest = { version = "^0.3.0", python = "^3.6" }
diff --git a/tests/conftest.py b/tests/conftest.py
index 08d4641b47c..098cf0df852 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -2,42 +2,19 @@
 import shutil
 import tempfile
 
-from typing import Any
-from typing import Dict
-
 import httpretty
 import pytest
 
-from poetry.config.config import Config as BaseConfig
 from poetry.config.dict_config_source import DictConfigSource
 from poetry.inspection.info import PackageInfo
 from poetry.utils._compat import Path
 from poetry.utils.env import EnvManager
 from poetry.utils.env import VirtualEnv
+from tests.helpers import Config
 from tests.helpers import mock_clone
 from tests.helpers import mock_download
 
 
-class Config(BaseConfig):
-    def get(self, setting_name, default=None):  # type: (str, Any) -> Any
-        self.merge(self._config_source.config)
-        self.merge(self._auth_config_source.config)
-
-        return super(Config, self).get(setting_name, default=default)
-
-    def raw(self):  # type: () -> Dict[str, Any]
-        self.merge(self._config_source.config)
-        self.merge(self._auth_config_source.config)
-
-        return super(Config, self).raw()
-
-    def all(self):  # type: () -> Dict[str, Any]
-        self.merge(self._config_source.config)
-        self.merge(self._auth_config_source.config)
-
-        return super(Config, self).all()
-
-
 @pytest.fixture
 def config_source():
     source = DictConfigSource()
diff --git a/tests/console/commands/test_add.py b/tests/console/commands/test_add.py
index 14b99842231..7cd987cb134 100644
--- a/tests/console/commands/test_add.py
+++ b/tests/console/commands/test_add.py
@@ -5,10 +5,7 @@
 
 import pytest
 
-from cleo.testers import CommandTester
-
 from poetry.core.semver import Version
-from poetry.installation.installer import Installer
 from poetry.repositories.legacy_repository import LegacyRepository
 from poetry.utils._compat import Path
 from tests.helpers import get_dependency
@@ -16,25 +13,8 @@
 
 
 @pytest.fixture()
-def tester(app, poetry, config, executor, env):
-    tester = CommandTester(app.find("add"))
-
-    executor._io = tester.io
-
-    installer = Installer(
-        tester.io,
-        env,
-        poetry.package,
-        poetry.locker,
-        poetry.pool,
-        config,
-        executor=executor,
-    )
-    installer.use_executor(True)
-    tester._command.set_installer(installer)
-    tester._command.set_env(env)
-
-    return tester
+def tester(poetry, app, make_installer_command_tester):
+    return make_installer_command_tester(poetry, "add", app)
 
 
 @pytest.fixture()
diff --git a/tests/console/commands/test_build.py b/tests/console/commands/test_build.py
new file mode 100644
index 00000000000..f4d9781f2f6
--- /dev/null
+++ b/tests/console/commands/test_build.py
@@ -0,0 +1,83 @@
+import re
+
+import pytest
+
+from tests.helpers import get_package
+
+
+@pytest.fixture
+def command_tester_with_build_requires(
+    repo, make_poetry, make_installer_command_tester
+):
+    repo.add_package(get_package("cython", "0.29.6"))
+    poetry = make_poetry("project_with_build_system_requires")
+    return make_installer_command_tester(poetry, "build")
+
+
+@pytest.fixture
+def command_tester(project_directory, make_poetry, make_installer_command_tester):
+    return make_installer_command_tester(make_poetry(project_directory), "build")
+
+
+def test_build_project_complete(command_tester):
+    tester = command_tester
+    command_tester.execute()
+
+    assert tester._command.installer.executor.installations_count == 0
+
+    output = tester.io.fetch_output()
+
+    assert "Writing lock file" not in output
+    assert "Building sdist" in output
+    assert "Built simple-project-1.2.3.tar.gz" in output
+    assert "Building wheel" in output
+    assert re.search(r"Built simple_project-1\.2\.3-.*\.whl", output) is not None
+
+
+def test_build_project_sdist(command_tester):
+    tester = command_tester
+    command_tester.execute("-f sdist")
+
+    assert tester._command.installer.executor.installations_count == 0
+
+    output = tester.io.fetch_output()
+
+    assert "Writing lock file" not in output
+    assert "Building sdist" in output
+    assert "Built simple-project-1.2.3.tar.gz" in output
+    assert "Building wheel" not in output
+    assert re.search(r"Built simple_project-1\.2\.3-.*\.whl", output) is None
+
+
+def test_build_project_wheel(command_tester):
+    tester = command_tester
+    command_tester.execute("-f wheel")
+
+    assert tester._command.installer.executor.installations_count == 0
+
+    output = tester.io.fetch_output()
+
+    assert "Writing lock file" not in output
+    assert "Building sdist" not in output
+    assert "Built simple-project-1.2.3.tar.gz" not in output
+    assert "Building wheel" in output
+    assert re.search(r"Built simple_project-1\.2\.3-.*\.whl", output) is not None
+
+
+def test_build_project_with_build_requires(command_tester_with_build_requires):
+    tester = command_tester_with_build_requires
+    tester.execute()
+
+    assert tester._command.installer.executor.installations_count == 1
+
+    package = tester._command.installer.executor._installs[0]
+    assert package.name == "cython"
+    assert package.version.text == "0.29.6"
+
+    output = tester.io.fetch_output()
+
+    assert "Writing lock file" in output
+    assert "Building sdist" in output
+    assert "Built project-1.2.3.tar.gz" in output
+    assert "Building wheel" in output
+    assert re.search(r"Built project-1\.2\.3-.*\.whl", output) is not None
diff --git a/tests/console/commands/test_export.py b/tests/console/commands/test_export.py
index 65d4927916d..b6e2e4e58f2 100644
--- a/tests/console/commands/test_export.py
+++ b/tests/console/commands/test_export.py
@@ -9,9 +9,9 @@
 from poetry.repositories.pool import Pool
 from tests.helpers import get_package
 
-from ..conftest import Application
-from ..conftest import Locker
 from ..conftest import Path
+from ..helpers import Application
+from ..helpers import Locker
 
 
 PYPROJECT_CONTENT = """\
diff --git a/tests/console/conftest.py b/tests/console/conftest.py
index 034e47207f5..582471f5223 100644
--- a/tests/console/conftest.py
+++ b/tests/console/conftest.py
@@ -1,65 +1,28 @@
 import os
 import re
+import shutil
 
 import pytest
 
 from cleo import ApplicationTester
+from cleo import CommandTester
 
-from poetry.console import Application as BaseApplication
-from poetry.core.masonry.utils.helpers import escape_name
-from poetry.core.masonry.utils.helpers import escape_version
-from poetry.core.packages.utils.link import Link
 from poetry.factory import Factory
-from poetry.installation.executor import Executor as BaseExecutor
+from poetry.installation import Installer
 from poetry.installation.noop_installer import NoopInstaller
 from poetry.io.null_io import NullIO
-from poetry.packages import Locker as BaseLocker
-from poetry.poetry import Poetry as BasePoetry
 from poetry.repositories import Pool
 from poetry.repositories import Repository as BaseRepository
-from poetry.repositories.exceptions import PackageNotFound
 from poetry.utils._compat import Path
 from poetry.utils.env import MockEnv
-from poetry.utils.toml_file import TomlFile
+from tests.console.helpers import Application
+from tests.console.helpers import Locker
+from tests.console.helpers import Repository
+from tests.helpers import Executor
+from tests.helpers import fixture
 from tests.helpers import mock_clone
 
 
-class Executor(BaseExecutor):
-    def __init__(self, *args, **kwargs):
-        super(Executor, self).__init__(*args, **kwargs)
-
-        self._installs = []
-        self._updates = []
-        self._uninstalls = []
-
-    @property
-    def installations(self):
-        return self._installs
-
-    @property
-    def updates(self):
-        return self._updates
-
-    @property
-    def removals(self):
-        return self._uninstalls
-
-    def _do_execute_operation(self, operation):
-        super(Executor, self)._do_execute_operation(operation)
-
-        if not operation.skipped:
-            getattr(self, "_{}s".format(operation.job_type)).append(operation.package)
-
-    def _execute_install(self, operation):
-        return 0
-
-    def _execute_update(self, operation):
-        return 0
-
-    def _execute_remove(self, operation):
-        return 0
-
-
 @pytest.fixture()
 def installer():
     return NoopInstaller()
@@ -114,104 +77,66 @@ def setup(mocker, installer, installed, config, env):
     os.environ.update(environ)
 
 
-class Application(BaseApplication):
-    def __init__(self, poetry):
-        super(Application, self).__init__()
-
-        self._poetry = poetry
-
-    def reset_poetry(self):
-        poetry = self._poetry
-        self._poetry = Factory().create_poetry(self._poetry.file.path.parent)
-        self._poetry.set_pool(poetry.pool)
-        self._poetry.set_config(poetry.config)
-        self._poetry.set_locker(
-            Locker(poetry.locker.lock.path, self._poetry.local_config)
-        )
-
-
-class Locker(BaseLocker):
-    def __init__(self, lock, local_config):
-        self._lock = TomlFile(lock)
-        self._local_config = local_config
-        self._lock_data = None
-        self._content_hash = self._get_content_hash()
-        self._locked = False
-        self._lock_data = None
-        self._write = False
-
-    def write(self, write=True):
-        self._write = write
-
-    def is_locked(self):
-        return self._locked
-
-    def locked(self, is_locked=True):
-        self._locked = is_locked
-
-        return self
-
-    def mock_lock_data(self, data):
-        self.locked()
-
-        self._lock_data = data
+@pytest.fixture
+def repo(http):
+    http.register_uri(
+        http.GET, re.compile("^https?://foo.bar/(.+?)$"),
+    )
+    return Repository(name="foo")
 
-    def is_fresh(self):
-        return True
 
-    def _write_lock_data(self, data):
-        if self._write:
-            super(Locker, self)._write_lock_data(data)
-            self._locked = True
-            return
+@pytest.fixture
+def project_directory():
+    return "simple_project"
 
-        self._lock_data = data
 
+@pytest.fixture
+def make_poetry(tmp_dir, repo, config):
+    def make_poetry_from_fixture_name(name):
+        src = fixture(name)
+        dst = Path(tmp_dir) / name
+        shutil.copytree(src.as_posix(), dst.as_posix())
 
-class Poetry(BasePoetry):
-    def __init__(self, file, local_config, package, locker, config):
-        self._file = TomlFile(file)
-        self._package = package
-        self._local_config = local_config
-        self._locker = Locker(locker.lock.path, locker._local_config)
-        self._config = config
+        poetry = Factory().create_poetry(dst)
+        poetry.set_locker(Locker(poetry.locker.lock.path, poetry.locker._local_config))
+        poetry.set_config(config)
 
-        # Configure sources
-        self._pool = Pool()
+        pool = Pool()
+        pool.add_repository(repo)
+        poetry.set_pool(pool)
 
+        return poetry
 
-class Repository(BaseRepository):
-    def find_packages(
-        self, name, constraint=None, extras=None, allow_prereleases=False
-    ):
-        packages = super(Repository, self).find_packages(
-            name, constraint, extras, allow_prereleases
-        )
-        if len(packages) == 0:
-            raise PackageNotFound("Package [{}] not found.".format(name))
-        return packages
-
-    def find_links_for_package(self, package):
-        return [
-            Link(
-                "https://foo.bar/files/{}-{}-py2.py3-none-any.whl".format(
-                    escape_name(package.name), escape_version(package.version.text)
-                )
-            )
-        ]
+    return make_poetry_from_fixture_name
 
 
 @pytest.fixture
-def repo(http):
-    http.register_uri(
-        http.GET, re.compile("^https?://foo.bar/(.+?)$"),
-    )
-    return Repository(name="foo")
+def make_installer_command_tester(config, executor, env):
+    def make_tester(poetry, command, app=None):
+        if app is None:
+            app = Application(poetry)
+            app.config.set_terminate_after_run(False)
+
+        tester = CommandTester(app.find(command))
+
+        executor._io = tester.io
+
+        installer = Installer(
+            tester.io,
+            env,
+            poetry.package,
+            poetry.locker,
+            poetry.pool,
+            config,
+            executor=executor,
+        )
+        installer.use_executor(True)
+        tester._command.set_installer(installer)
+        tester._command.set_env(env)
 
+        return tester
 
-@pytest.fixture
-def project_directory():
-    return "simple_project"
+    yield make_tester
 
 
 @pytest.fixture
diff --git a/tests/console/helpers.py b/tests/console/helpers.py
new file mode 100644
index 00000000000..b0f845c6500
--- /dev/null
+++ b/tests/console/helpers.py
@@ -0,0 +1,84 @@
+from poetry.console import Application as BaseApplication
+from poetry.core.masonry.utils.helpers import escape_name
+from poetry.core.masonry.utils.helpers import escape_version
+from poetry.core.packages import Link
+from poetry.factory import Factory
+from poetry.packages import Locker as BaseLocker
+from poetry.repositories import Repository as BaseRepository
+from poetry.repositories.exceptions import PackageNotFound
+from poetry.utils.toml_file import TomlFile
+
+
+class Application(BaseApplication):
+    def __init__(self, poetry):
+        super(Application, self).__init__()
+
+        self._poetry = poetry
+
+    def reset_poetry(self):
+        poetry = self._poetry
+        self._poetry = Factory().create_poetry(self._poetry.file.path.parent)
+        self._poetry.set_pool(poetry.pool)
+        self._poetry.set_config(poetry.config)
+        self._poetry.set_locker(
+            Locker(poetry.locker.lock.path, self._poetry.local_config)
+        )
+
+
+class Locker(BaseLocker):
+    def __init__(self, lock, local_config):
+        self._lock = TomlFile(lock)
+        self._local_config = local_config
+        self._lock_data = None
+        self._content_hash = self._get_content_hash()
+        self._locked = False
+        self._lock_data = None
+        self._write = False
+
+    def write(self, write=True):
+        self._write = write
+
+    def is_locked(self):
+        return self._locked
+
+    def locked(self, is_locked=True):
+        self._locked = is_locked
+
+        return self
+
+    def mock_lock_data(self, data):
+        self.locked()
+
+        self._lock_data = data
+
+    def is_fresh(self):
+        return True
+
+    def _write_lock_data(self, data):
+        if self._write:
+            super(Locker, self)._write_lock_data(data)
+            self._locked = True
+            return
+
+        self._lock_data = data
+
+
+class Repository(BaseRepository):
+    def find_packages(
+        self, name, constraint=None, extras=None, allow_prereleases=False
+    ):
+        packages = super(Repository, self).find_packages(
+            name, constraint, extras, allow_prereleases
+        )
+        if len(packages) == 0:
+            raise PackageNotFound("Package [{}] not found.".format(name))
+        return packages
+
+    def find_links_for_package(self, package):
+        return [
+            Link(
+                "https://foo.bar/files/{}-{}-py2.py3-none-any.whl".format(
+                    escape_name(package.name), escape_version(package.version.text)
+                )
+            )
+        ]
diff --git a/tests/fixtures/project_with_build_system_requires/README.rst b/tests/fixtures/project_with_build_system_requires/README.rst
new file mode 100644
index 00000000000..f7fe15470f9
--- /dev/null
+++ b/tests/fixtures/project_with_build_system_requires/README.rst
@@ -0,0 +1,2 @@
+My Package
+==========
diff --git a/tests/fixtures/project_with_build_system_requires/build.py b/tests/fixtures/project_with_build_system_requires/build.py
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/tests/fixtures/project_with_build_system_requires/project/__init__.py b/tests/fixtures/project_with_build_system_requires/project/__init__.py
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/tests/fixtures/project_with_build_system_requires/pyproject.toml b/tests/fixtures/project_with_build_system_requires/pyproject.toml
new file mode 100644
index 00000000000..65f884a70ba
--- /dev/null
+++ b/tests/fixtures/project_with_build_system_requires/pyproject.toml
@@ -0,0 +1,19 @@
+[tool.poetry]
+name = "project"
+version = "1.2.3"
+description = "Some description."
+authors = []
+license = "MIT"
+
+[tool.poetry.build]
+script = "build.py"
+generate-setup-file = false
+
+[tool.poetry.dependencies]
+python = "^3.7"
+
+[build-system]
+requires = [
+  "poetry-core",
+  "Cython>=0.29.6",
+]
diff --git a/tests/helpers.py b/tests/helpers.py
index 0dd7ce312e5..01c1a485e69 100644
--- a/tests/helpers.py
+++ b/tests/helpers.py
@@ -1,9 +1,14 @@
 import os
 import shutil
 
+from typing import Any
+from typing import Dict
+
+from poetry.config.config import Config as BaseConfig
 from poetry.core.packages import Dependency
 from poetry.core.packages import Package
 from poetry.core.vcs.git import ParsedUrl
+from poetry.installation.executor import Executor as BaseExecutor
 from poetry.utils._compat import PY2
 from poetry.utils._compat import WINDOWS
 from poetry.utils._compat import Path
@@ -13,6 +18,26 @@
 FIXTURE_PATH = Path(__file__).parent / "fixtures"
 
 
+class Config(BaseConfig):
+    def get(self, setting_name, default=None):  # type: (str, Any) -> Any
+        self.merge(self._config_source.config)
+        self.merge(self._auth_config_source.config)
+
+        return super(Config, self).get(setting_name, default=default)
+
+    def raw(self):  # type: () -> Dict[str, Any]
+        self.merge(self._config_source.config)
+        self.merge(self._auth_config_source.config)
+
+        return super(Config, self).raw()
+
+    def all(self):  # type: () -> Dict[str, Any]
+        self.merge(self._config_source.config)
+        self.merge(self._auth_config_source.config)
+
+        return super(Config, self).all()
+
+
 def get_package(name, version):
     return Package(name, version)
 
@@ -88,3 +113,39 @@ def mock_download(url, dest, **__):
     fixture = fixtures / parts.path.lstrip("/")
 
     copy_or_symlink(fixture, Path(dest))
+
+
+class Executor(BaseExecutor):
+    def __init__(self, *args, **kwargs):
+        super(Executor, self).__init__(*args, **kwargs)
+
+        self._installs = []
+        self._updates = []
+        self._uninstalls = []
+
+    @property
+    def installations(self):
+        return self._installs
+
+    @property
+    def updates(self):
+        return self._updates
+
+    @property
+    def removals(self):
+        return self._uninstalls
+
+    def _do_execute_operation(self, operation):
+        super(Executor, self)._do_execute_operation(operation)
+
+        if not operation.skipped:
+            getattr(self, "_{}s".format(operation.job_type)).append(operation.package)
+
+    def _execute_install(self, operation):
+        return 0
+
+    def _execute_update(self, operation):
+        return 0
+
+    def _execute_remove(self, operation):
+        return 0
diff --git a/tests/installation/test_installer.py b/tests/installation/test_installer.py
index 88103e7c323..067f18ee977 100644
--- a/tests/installation/test_installer.py
+++ b/tests/installation/test_installer.py
@@ -8,7 +8,6 @@
 
 from poetry.core.packages import ProjectPackage
 from poetry.installation import Installer as BaseInstaller
-from poetry.installation.executor import Executor as BaseExecutor
 from poetry.installation.noop_installer import NoopInstaller
 from poetry.packages import Locker as BaseLocker
 from poetry.repositories import Pool
@@ -19,6 +18,7 @@
 from poetry.utils.env import MockEnv
 from poetry.utils.env import NullEnv
 from poetry.utils.toml_file import TomlFile
+from tests.helpers import Executor
 from tests.helpers import get_dependency
 from tests.helpers import get_package
 from tests.repositories.test_legacy_repository import (
@@ -35,42 +35,6 @@ def _get_installer(self):
         return NoopInstaller()
 
 
-class Executor(BaseExecutor):
-    def __init__(self, *args, **kwargs):
-        super(Executor, self).__init__(*args, **kwargs)
-
-        self._installs = []
-        self._updates = []
-        self._uninstalls = []
-
-    @property
-    def installations(self):
-        return self._installs
-
-    @property
-    def updates(self):
-        return self._updates
-
-    @property
-    def removals(self):
-        return self._uninstalls
-
-    def _do_execute_operation(self, operation):
-        super(Executor, self)._do_execute_operation(operation)
-
-        if not operation.skipped:
-            getattr(self, "_{}s".format(operation.job_type)).append(operation.package)
-
-    def _execute_install(self, operation):
-        return 0
-
-    def _execute_update(self, operation):
-        return 0
-
-    def _execute_uninstall(self, operation):
-        return 0
-
-
 class CustomInstalledRepository(InstalledRepository):
     @classmethod
     def load(cls, env):
diff --git a/tests/puzzle/test_solver.py b/tests/puzzle/test_solver.py
index a3678c43bd4..c3540a36591 100644
--- a/tests/puzzle/test_solver.py
+++ b/tests/puzzle/test_solver.py
@@ -902,12 +902,14 @@ def test_solver_can_resolve_git_dependencies(solver, repo, package):
 
     ops = solver.solve()
 
+    demo = get_package("demo", "0.1.2")
+    demo.source_type = "git"
+    demo.source_url = "https://github.com/demo/demo.git"
+    demo.source_reference = "9cf87a285a2d3fbb0b9fa621997b3acc3631ed24"
+
     check_solver_result(
         ops,
-        [
-            {"job": "install", "package": pendulum},
-            {"job": "install", "package": get_package("demo", "0.1.2")},
-        ],
+        [{"job": "install", "package": pendulum}, {"job": "install", "package": demo}],
     )
 
     op = ops[1]
@@ -928,12 +930,17 @@ def test_solver_can_resolve_git_dependencies_with_extras(solver, repo, package):
 
     ops = solver.solve()
 
+    demo = get_package("demo", "0.1.2")
+    demo.source_type = "git"
+    demo.source_url = "https://github.com/demo/demo.git"
+    demo.source_reference = "9cf87a285a2d3fbb0b9fa621997b3acc3631ed24"
+
     check_solver_result(
         ops,
         [
             {"job": "install", "package": cleo},
             {"job": "install", "package": pendulum},
-            {"job": "install", "package": get_package("demo", "0.1.2")},
+            {"job": "install", "package": demo},
         ],
     )
 
@@ -949,7 +956,12 @@ def test_solver_can_resolve_git_dependencies_with_ref(solver, repo, package, ref
     repo.add_package(pendulum)
     repo.add_package(cleo)
 
-    git_config = {"git": "https://github.com/demo/demo.git"}
+    demo = get_package("demo", "0.1.2")
+    demo.source_type = "git"
+    demo.source_url = "https://github.com/demo/demo.git"
+    demo.source_reference = "9cf87a285a2d3fbb0b9fa621997b3acc3631ed24"
+
+    git_config = {demo.source_type: demo.source_url}
     git_config.update(ref)
     package.add_dependency("demo", git_config)
 
@@ -957,10 +969,7 @@ def test_solver_can_resolve_git_dependencies_with_ref(solver, repo, package, ref
 
     check_solver_result(
         ops,
-        [
-            {"job": "install", "package": pendulum},
-            {"job": "install", "package": get_package("demo", "0.1.2")},
-        ],
+        [{"job": "install", "package": pendulum}, {"job": "install", "package": demo}],
     )
 
     op = ops[1]
@@ -1206,25 +1215,26 @@ def test_solver_git_dependencies_update(solver, repo, package, installed):
     repo.add_package(pendulum)
     repo.add_package(cleo)
 
-    demo = get_package("demo", "0.1.2")
-    demo.source_type = "git"
-    demo.source_url = "https://github.com/demo/demo.git"
-    demo.source_reference = "123456"
-    installed.add_package(demo)
+    demo_installed = get_package("demo", "0.1.2")
+    demo_installed.source_type = "git"
+    demo_installed.source_url = "https://github.com/demo/demo.git"
+    demo_installed.source_reference = "123456"
+    installed.add_package(demo_installed)
 
     package.add_dependency("demo", {"git": "https://github.com/demo/demo.git"})
 
     ops = solver.solve()
 
+    demo = get_package("demo", "0.1.2")
+    demo.source_type = "git"
+    demo.source_url = "https://github.com/demo/demo.git"
+    demo.source_reference = "9cf87a285a2d3fbb0b9fa621997b3acc3631ed24"
+
     check_solver_result(
         ops,
         [
             {"job": "install", "package": pendulum},
-            {
-                "job": "update",
-                "from": get_package("demo", "0.1.2"),
-                "to": get_package("demo", "0.1.2"),
-            },
+            {"job": "update", "from": demo_installed, "to": demo},
         ],
     )
 
@@ -1256,11 +1266,7 @@ def test_solver_git_dependencies_update_skipped(solver, repo, package, installed
         ops,
         [
             {"job": "install", "package": pendulum},
-            {
-                "job": "install",
-                "package": get_package("demo", "0.1.2"),
-                "skipped": True,
-            },
+            {"job": "install", "package": demo, "skipped": True},
         ],
     )
 
@@ -1289,11 +1295,7 @@ def test_solver_git_dependencies_short_hash_update_skipped(
         ops,
         [
             {"job": "install", "package": pendulum},
-            {
-                "job": "install",
-                "package": get_package("demo", "0.1.2"),
-                "skipped": True,
-            },
+            {"job": "install", "package": demo, "skipped": True},
         ],
     )
 
@@ -1315,12 +1317,13 @@ def test_solver_can_resolve_directory_dependencies(solver, repo, package):
 
     ops = solver.solve()
 
+    demo = get_package("demo", "0.1.2")
+    demo.source_type = "directory"
+    demo.source_url = path
+
     check_solver_result(
         ops,
-        [
-            {"job": "install", "package": pendulum},
-            {"job": "install", "package": get_package("demo", "0.1.2")},
-        ],
+        [{"job": "install", "package": pendulum}, {"job": "install", "package": demo}],
     )
 
     op = ops[1]
@@ -1350,12 +1353,16 @@ def test_solver_can_resolve_directory_dependencies_with_extras(solver, repo, pac
 
     ops = solver.solve()
 
+    demo = get_package("demo", "0.1.2")
+    demo.source_type = "directory"
+    demo.source_url = path
+
     check_solver_result(
         ops,
         [
             {"job": "install", "package": cleo},
             {"job": "install", "package": pendulum},
-            {"job": "install", "package": get_package("demo", "0.1.2")},
+            {"job": "install", "package": demo},
         ],
     )
 
@@ -1382,12 +1389,13 @@ def test_solver_can_resolve_sdist_dependencies(solver, repo, package):
 
     ops = solver.solve()
 
+    demo = get_package("demo", "0.1.0")
+    demo.source_type = "file"
+    demo.source_url = path
+
     check_solver_result(
         ops,
-        [
-            {"job": "install", "package": pendulum},
-            {"job": "install", "package": get_package("demo", "0.1.0")},
-        ],
+        [{"job": "install", "package": pendulum}, {"job": "install", "package": demo}],
     )
 
     op = ops[1]
@@ -1415,12 +1423,16 @@ def test_solver_can_resolve_sdist_dependencies_with_extras(solver, repo, package
 
     ops = solver.solve()
 
+    demo = get_package("demo", "0.1.0")
+    demo.source_type = "file"
+    demo.source_url = path
+
     check_solver_result(
         ops,
         [
             {"job": "install", "package": cleo},
             {"job": "install", "package": pendulum},
-            {"job": "install", "package": get_package("demo", "0.1.0")},
+            {"job": "install", "package": demo},
         ],
     )
 
@@ -1447,12 +1459,13 @@ def test_solver_can_resolve_wheel_dependencies(solver, repo, package):
 
     ops = solver.solve()
 
+    demo = get_package("demo", "0.1.0")
+    demo.source_type = "file"
+    demo.source_url = path
+
     check_solver_result(
         ops,
-        [
-            {"job": "install", "package": pendulum},
-            {"job": "install", "package": get_package("demo", "0.1.0")},
-        ],
+        [{"job": "install", "package": pendulum}, {"job": "install", "package": demo}],
     )
 
     op = ops[1]
@@ -1480,12 +1493,16 @@ def test_solver_can_resolve_wheel_dependencies_with_extras(solver, repo, package
 
     ops = solver.solve()
 
+    demo = get_package("demo", "0.1.0")
+    demo.source_type = "file"
+    demo.source_url = path
+
     check_solver_result(
         ops,
         [
             {"job": "install", "package": cleo},
             {"job": "install", "package": pendulum},
-            {"job": "install", "package": get_package("demo", "0.1.0")},
+            {"job": "install", "package": demo},
         ],
     )