diff --git a/src/env_fake.cpp b/src/env_fake.cpp
new file mode 100644
index 0000000..d859629
--- /dev/null
+++ b/src/env_fake.cpp
@@ -0,0 +1,129 @@
+/* Copyright 2020, Michele Santullo
+ * This file is part of user-gcc.
+ *
+ * User-gcc is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * User-gcc is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with user-gcc.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "env_fake.hpp"
+#include "to_var_map.hpp"
+#include "safe_print.hpp"
+#include "string_view_cat.hpp"
+#include <unistd.h>
+#include <utility>
+#include <optional>
+#include <type_traits>
+#include <cassert>
+#include <algorithm>
+
+namespace duck {
+namespace {
+	template <
+		typename M,
+		typename I,
+		typename F,
+		typename R=decltype(std::declval<F>()(std::declval<decltype(std::declval<M>().find(std::declval<I>()))&>())),
+		//not supposed to be altered by the caller
+		bool FIsNoex=noexcept(std::declval<F>()(std::declval<decltype(std::declval<M>().find(std::declval<I>()))&>())) and noexcept(R())
+	>
+	R run_if_found (M& map, const I& item, F func) noexcept(FIsNoex) {
+		typedef decltype(map.find(item)) iterator_type;
+
+		iterator_type it_found;
+		if constexpr (FIsNoex) {
+			try {
+				it_found = map.find(item);
+			}
+			catch (...) {
+				safe_print_error("Unexpected exception in run_if_found() will be ignored");
+			}
+		}
+		else {
+			it_found = map.find(item);
+		}
+
+		if constexpr (std::is_same<R, void>::value) {
+			if (map.end() != it_found) {
+				func(it_found);
+			}
+		}
+		else {
+			if (map.end() != it_found) {
+				return func(it_found);
+			}
+			else {
+				return R{};
+			}
+		}
+	}
+} //unnamed namespace
+
+EnvFake::EnvFake (bool starts_empty) :
+	m_map_strong_cpy(),
+	m_map(starts_empty ? map_type() : to_var_map_ignore_ownership(environ))
+{
+}
+
+std::optional<std::string_view> EnvFake::get (std::string_view name) const noexcept {
+	return run_if_found(m_map, name, [](auto& it)noexcept{return std::make_optional(it->second);});
+}
+
+std::string_view EnvFake::get (std::string_view name, std::string_view def) const noexcept {
+	bool ret_def{true};
+	std::string_view maybe_ret(run_if_found(m_map, name, [&ret_def](auto& it)noexcept{ret_def=false; return it->second;}));
+	if (ret_def)
+		return def;
+	else
+		return maybe_ret;
+}
+
+void EnvFake::set (std::string_view name, std::string_view value) {
+	assert(not name.empty());
+	if (name.empty())
+		return;
+
+	const std::size_t size = name.size() + value.size();
+	std::unique_ptr<char[]> buff = std::make_unique<char[]>(size);
+	std::copy(name.begin(), name.end(), buff.get());
+	std::copy(value.begin(), value.end(), buff.get() + name.size());
+
+	const std::string_view new_name(buff.get(), name.size());
+	assert(new_name == name);
+	const std::string_view new_value(buff.get() + name.size(), value.size());
+	assert(new_value == value);
+
+	m_map_strong_cpy.insert_or_assign(std::string_view(new_name), std::move(buff));
+	m_map.insert_or_assign(std::string_view(new_name), std::string_view(new_value));
+	assert(m_map.at(name) == value);
+	assert(m_map.find(name)->first.data() == new_name.data());
+}
+
+void EnvFake::unset (std::string_view name) noexcept {
+	run_if_found(m_map, name, [&](auto& it)noexcept{m_map.erase(it);});
+	run_if_found(m_map_strong_cpy, name, [&](auto& it)noexcept{m_map_strong_cpy.erase(it);});
+}
+
+bool EnvFake::is_set (std::string_view name) const noexcept {
+	return run_if_found(m_map, name, [](auto&)noexcept{return true;});
+}
+
+auto EnvFake::size() const noexcept -> size_type {
+	return m_map.size();
+}
+
+void EnvFake::clear() noexcept {
+	m_map.clear();
+	m_map_strong_cpy.clear();
+}
+
+} //namespace duck
diff --git a/src/env_fake.hpp b/src/env_fake.hpp
new file mode 100644
index 0000000..75fd1f8
--- /dev/null
+++ b/src/env_fake.hpp
@@ -0,0 +1,43 @@
+/* Copyright 2020, Michele Santullo
+ * This file is part of user-gcc.
+ *
+ * User-gcc is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * User-gcc is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with user-gcc.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include "env_base.hpp"
+#include <unordered_map>
+#include <memory>
+
+namespace duck {
+	class EnvFake : public EnvBase {
+		typedef std::unordered_map<std::string_view, std::string_view> map_type;
+	public:
+		explicit EnvFake (bool starts_empty=false);
+		~EnvFake() noexcept = default;
+
+		virtual std::optional<std::string_view> get (std::string_view name) const noexcept override;
+		virtual std::string_view get (std::string_view name, std::string_view def) const noexcept override;
+		virtual void set (std::string_view name, std::string_view value) override;
+		virtual void unset (std::string_view name) noexcept override;
+		virtual bool is_set (std::string_view name) const noexcept override;
+		virtual size_type size() const noexcept override;
+		virtual void clear() noexcept override;
+
+	private:
+		std::unordered_map<std::string_view, std::unique_ptr<char[]>> m_map_strong_cpy;
+		map_type m_map;
+	};
+} //namespace duck
diff --git a/src/meson.build b/src/meson.build
index 8a762d8..2f547ed 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -21,6 +21,7 @@ executable(meson.project_name(),
 	'var_map.cpp',
 	'env_base.cpp',
 	'env_real.cpp',
+	'env_fake.cpp',
 	'safe_print.cpp',
 	install: true,
 	dependencies: [fslib_dep],