diff --git a/examples/README.md b/examples/README.md
index c035d11f..08e92b7e 100644
--- a/examples/README.md
+++ b/examples/README.md
@@ -61,7 +61,7 @@ Each of these examples demonstrates one aspect or feature of bashly.
 - [yaml](yaml#readme) - using the YAML reading functions
 - [colors](colors#readme) - using the color print feature
 - [completions](completions#readme) - adding bash completion functionality
-- [validations](validations#readme) - adding argument validation functions
+- [validations](validations#readme) - adding validation functions for arguments, flags or environment variables
 - [hooks](hooks#readme) - adding before/after hooks
 
 ## Real-world-like examples
diff --git a/examples/needs/README.md b/examples/needs/README.md
index a3ff0b50..d3825211 100644
--- a/examples/needs/README.md
+++ b/examples/needs/README.md
@@ -83,7 +83,7 @@ Options:
 ### `$ ./cli --add deploy`
 
 ````shell
---add requires --command
+--add needs --command
 
 
 ````
@@ -91,7 +91,7 @@ Options:
 ### `$ ./cli --add deploy --command 'git push'`
 
 ````shell
---add requires --target
+--add needs --target
 
 
 ````
diff --git a/examples/validations/README.md b/examples/validations/README.md
index 9b436fb4..75c72c47 100644
--- a/examples/validations/README.md
+++ b/examples/validations/README.md
@@ -50,6 +50,15 @@ commands:
 
     # Validations also work on flags (when they have arguments)
     validate: file_exists
+
+- name: build
+  environment_variables:
+  - name: build_dir
+    help: Path to the build directory
+    default: release
+
+    # Validations also work on environment variables
+    validate: dir_exists
 ````
 
 
@@ -97,5 +106,28 @@ must be an existing file
 
 ````
 
+### `$ ./validate build`
+
+````shell
+validation error in environment variable BUILD_DIR:
+must be an existing directory
+
+
+````
+
+### `$ BUILD_DIR=src ./validate build`
+
+````shell
+# this file is located in 'src/build_command.sh'
+# code for 'validate build' goes here
+# you can edit it freely and regenerate (it will not be overwritten)
+args: none
+
+environment variables:
+- $BUILD_DIR = src
+
+
+````
+
 
 
diff --git a/examples/validations/src/bashly.yml b/examples/validations/src/bashly.yml
index 058e6df2..ae6c3ce8 100644
--- a/examples/validations/src/bashly.yml
+++ b/examples/validations/src/bashly.yml
@@ -27,3 +27,11 @@ commands:
     # Validations also work on flags (when they have arguments)
     validate: file_exists
 
+- name: build
+  environment_variables:
+  - name: build_dir
+    help: Path to the build directory
+    default: release
+
+    # Validations also work on environment variables
+    validate: dir_exists
diff --git a/examples/validations/src/build_command.sh b/examples/validations/src/build_command.sh
new file mode 100644
index 00000000..ec2f6d2b
--- /dev/null
+++ b/examples/validations/src/build_command.sh
@@ -0,0 +1,4 @@
+echo "# this file is located in 'src/build_command.sh'"
+echo "# code for 'validate build' goes here"
+echo "# you can edit it freely and regenerate (it will not be overwritten)"
+inspect_args
diff --git a/examples/validations/test.sh b/examples/validations/test.sh
index 83adb4eb..e0574e17 100644
--- a/examples/validations/test.sh
+++ b/examples/validations/test.sh
@@ -14,3 +14,6 @@ bashly generate
 ./validate calc A
 ./validate calc 1 B
 ./validate calc 1 2 --save no-such-file.txt
+
+./validate build
+BUILD_DIR=src ./validate build
\ No newline at end of file
diff --git a/lib/bashly/docs/env.yml b/lib/bashly/docs/env.yml
index 21246489..096cc0d5 100644
--- a/lib/bashly/docs/env.yml
+++ b/lib/bashly/docs/env.yml
@@ -49,6 +49,16 @@ environment_variable.required:
   help: Specify that this variable is required.
   url: https://bashly.dannyb.co/configuration/environment-variable/#required
   example: |-
+    environment_variables:
     - name: api_key
       help: Your API key
       required: true
+
+environment_variable.validate:
+  help: Apply custom validation functions.
+
+  url: https://bashly.dannyb.co/configuration/environment-variable/#validate
+  example: |-
+    environment_variables:
+    - name: build_dir
+      validate: dir_exists
diff --git a/lib/bashly/libraries/strings/strings.yml b/lib/bashly/libraries/strings/strings.yml
index 02f597ad..13834bed 100644
--- a/lib/bashly/libraries/strings/strings.yml
+++ b/lib/bashly/libraries/strings/strings.yml
@@ -42,3 +42,4 @@ disallowed_argument: "%{name} must be one of: %{allowed}"
 disallowed_environment_variable: "%{name} environment variable must be one of: %{allowed}"
 unsupported_bash_version: "bash version 4 or higher is required"
 validation_error: "validation error in %s:\\n%s"
+environment_variable_validation_error: "validation error in environment variable %s:\\n%s"
diff --git a/lib/bashly/script/environment_variable.rb b/lib/bashly/script/environment_variable.rb
index b86ab274..c60a041b 100644
--- a/lib/bashly/script/environment_variable.rb
+++ b/lib/bashly/script/environment_variable.rb
@@ -3,7 +3,9 @@ module Script
     class EnvironmentVariable < Base
       class << self
         def option_keys
-          @option_keys ||= %i[allowed default help name required private]
+          @option_keys ||= %i[
+            allowed default help name required private validate
+          ]
         end
       end
 
diff --git a/lib/bashly/script/introspection/environment_variables.rb b/lib/bashly/script/introspection/environment_variables.rb
index 0f2da004..512204f9 100644
--- a/lib/bashly/script/introspection/environment_variables.rb
+++ b/lib/bashly/script/introspection/environment_variables.rb
@@ -2,7 +2,7 @@ module Bashly
   module Script
     module Introspection
       module EnvironmentVariables
-        # Returns an array of all the default Environment Variables
+        # Returns an array of all the Environment Variables with default values
         def default_environment_variables
           environment_variables.select(&:default)
         end
@@ -26,6 +26,11 @@ def required_environment_variables
           environment_variables.select(&:required)
         end
 
+        # Returns an array of all the environment_variables with a validation
+        def validated_environment_variables
+          environment_variables.select(&:validate)
+        end
+
         # Returns an array of all the environment_variables with a whitelist arg
         def whitelisted_environment_variables
           environment_variables.select(&:allowed)
diff --git a/lib/bashly/script/introspection/flags.rb b/lib/bashly/script/introspection/flags.rb
index 07485664..81cea8cf 100644
--- a/lib/bashly/script/introspection/flags.rb
+++ b/lib/bashly/script/introspection/flags.rb
@@ -22,6 +22,11 @@ def global_flags?
           flags.any? and commands.any?
         end
 
+        # Returns an array of all fpags that need other flags
+        def needy_flags
+          flags.select(&:needs)
+        end
+
         # Returns only flags that are not private
         def public_flags
           flags.reject(&:private)
@@ -32,11 +37,6 @@ def required_flags
           flags.select(&:required)
         end
 
-        # Returns an array of all fpags that need other flags
-        def needy_flags
-          flags.select(&:needs)
-        end
-
         # Returns true if one of the flags matches the provided short code
         def short_flag_exist?(flag)
           flags.any? { |f| f.short == flag }
diff --git a/lib/bashly/views/command/environment_variables_filter.gtx b/lib/bashly/views/command/environment_variables_filter.gtx
index 666d9377..f95fdf87 100644
--- a/lib/bashly/views/command/environment_variables_filter.gtx
+++ b/lib/bashly/views/command/environment_variables_filter.gtx
@@ -24,3 +24,9 @@ if whitelisted_environment_variables.any?
     > fi
   end
 end
+
+if validated_environment_variables.any?
+  validated_environment_variables.each do |env_var|
+    = env_var.render(:validations)
+  end
+end
diff --git a/lib/bashly/views/environment_variable/validations.gtx b/lib/bashly/views/environment_variable/validations.gtx
new file mode 100644
index 00000000..805536cf
--- /dev/null
+++ b/lib/bashly/views/environment_variable/validations.gtx
@@ -0,0 +1,9 @@
+if validate
+  = view_marker
+
+  > if [[ -v {{ name.upcase }} && -n $(validate_{{ validate }} "${{ name.upcase }}") ]]; then
+  >   printf "{{ strings[:environment_variable_validation_error] }}\n" "{{ usage_string }}" "$(validate_{{ validate }} "${{ name.upcase }}")" >&2
+  >   exit 1
+  > fi
+  >
+end
diff --git a/schemas/bashly.json b/schemas/bashly.json
index c1a3f26b..441c42e7 100644
--- a/schemas/bashly.json
+++ b/schemas/bashly.json
@@ -334,6 +334,17 @@
           "type": "boolean",
           "default": true
         },
+        "validate": {
+          "title": "validate",
+          "description": "A validation function for the current environment variable\nhttps://bashly.dannyb.co/configuration/environment-variable/#validate",
+          "type": "string",
+          "examples": [
+            "file_exists",
+            "dir_exists",
+            "integer",
+            "non_empty"
+          ]
+        },
         "allowed": {
           "title": "allowed",
           "description": "Valid values of the current environment variable\nhttps://bashly.dannyb.co/configuration/environment-variable/#allowed",
diff --git a/schemas/strings.json b/schemas/strings.json
index b57df61a..60a864b9 100644
--- a/schemas/strings.json
+++ b/schemas/strings.json
@@ -241,6 +241,13 @@
             "type": "string",
             "minLength": 1,
             "default": "validation error in %s:\\n%s"
+        },
+        "environment_variable_validation_error": {
+            "title": "environment variable validation error",
+            "description": "The error message template for failed custom validation for environment variables\nhttps://bashly.dannyb.co/advanced/strings/#custom-strings",
+            "type": "string",
+            "minLength": 1,
+            "default": "validation error in environment variable %s:\\n%s"
         }
     },
     "additionalProperties": false
diff --git a/spec/approvals/cli/doc/full b/spec/approvals/cli/doc/full
index 18fe0697..67f56ae8 100644
--- a/spec/approvals/cli/doc/full
+++ b/spec/approvals/cli/doc/full
@@ -539,12 +539,23 @@ environment_variable.required
 
   Specify that this variable is required.
 
+    environment_variables:
     - name: api_key
       help: Your API key
       required: true
 
   See https://bashly.dannyb.co/configuration/environment-variable/#required
 
+environment_variable.validate
+
+  Apply custom validation functions.
+
+    environment_variables:
+    - name: build_dir
+      validate: dir_exists
+
+  See https://bashly.dannyb.co/configuration/environment-variable/#validate
+
 flag
 
   Define option flags.
diff --git a/spec/approvals/cli/doc/index b/spec/approvals/cli/doc/index
index d9d7d9d6..00791e68 100644
--- a/spec/approvals/cli/doc/index
+++ b/spec/approvals/cli/doc/index
@@ -34,6 +34,7 @@ environment_variable.help
 environment_variable.name
 environment_variable.private
 environment_variable.required
+environment_variable.validate
 flag
 flag.allowed
 flag.arg
diff --git a/spec/approvals/examples/validations b/spec/approvals/examples/validations
index 76b2085c..ffe232f9 100644
--- a/spec/approvals/examples/validations
+++ b/spec/approvals/examples/validations
@@ -6,6 +6,7 @@ created src/lib/validations/validate_not_empty.sh
 + bashly generate
 creating user files in src
 created src/calc_command.sh
+created src/build_command.sh
 created ./validate
 run ./validate --help to test your bash script
 + ./validate calc 1 2 --save README.md
@@ -25,3 +26,15 @@ must be an integer
 + ./validate calc 1 2 --save no-such-file.txt
 validation error in --save PATH:
 must be an existing file
++ ./validate build
+validation error in environment variable BUILD_DIR:
+must be an existing directory
++ BUILD_DIR=src
++ ./validate build
+# this file is located in 'src/build_command.sh'
+# code for 'validate build' goes here
+# you can edit it freely and regenerate (it will not be overwritten)
+args: none
+
+environment variables:
+- $BUILD_DIR = src
diff --git a/spec/bashly/script/command_spec.rb b/spec/bashly/script/command_spec.rb
index a096bbdb..f7d3adce 100644
--- a/spec/bashly/script/command_spec.rb
+++ b/spec/bashly/script/command_spec.rb
@@ -48,13 +48,6 @@
     end
   end
 
-  describe '#args' do
-    it 'returns an array of Argument objects' do
-      expect(subject.args).to be_an Array
-      expect(subject.args.first).to be_a Script::Argument
-    end
-  end
-
   describe '#caption_string' do
     it 'returns a string containing the name and summary' do
       expect(subject.caption_string).to eq 'get - get something from somewhere'
@@ -69,129 +62,6 @@
     end
   end
 
-  describe '#command_aliases' do
-    let(:fixture) { :aliases }
-
-    it 'returns an array of command aliases' do
-      expect(subject.command_aliases).to eq %w[download d pull upload u push update upgrade]
-    end
-  end
-
-  describe '#command_help_data' do
-    let(:fixture) { :exposed }
-
-    it 'returns a hash suitable for showing command and exposed subcommand help' do
-      expect(subject.command_help_data.to_yaml)
-        .to match_approval('script/command/exposed_commands')
-    end
-  end
-
-  describe '#command_names' do
-    let(:fixture) { :docker }
-
-    it 'returns an array of command names' do
-      expect(subject.command_names).to eq %w[container image]
-    end
-  end
-
-  describe '#commands' do
-    let(:fixture) { :docker }
-
-    it 'returns an array of Command objects' do
-      expect(subject.commands).to be_an Array
-      expect(subject.commands.first).to be_a described_class
-    end
-
-    it 'sets the parents property of its commands' do
-      expect(subject.commands.first.parents).to eq ['docker']
-    end
-  end
-
-  describe '#deep_commands' do
-    let(:fixture) { :docker }
-
-    it 'returns an array of all commands in the tree' do
-      expect(subject.deep_commands.map(&:full_name))
-        .to eq ['docker container', 'docker container run', 'docker container stop', 'docker image']
-    end
-
-    context 'when include_self is true' do
-      it 'prepends the result with the command itself' do
-        expect(subject.deep_commands(include_self: true).map(&:full_name))
-          .to eq ['docker', 'docker container', 'docker container run', 'docker container stop', 'docker image']
-      end
-    end
-  end
-
-  describe '#default_arguments' do
-    let(:fixture) { :default_values }
-
-    it 'returns an array of only the Argument objects that have default' do
-      expect(subject.default_args.size).to eq 1
-      expect(subject.default_args.first.name).to eq 'files'
-    end
-  end
-
-  describe '#default_command' do
-    let(:fixture) { :default_command }
-
-    it 'returns a Command object of the first default command' do
-      expect(subject.default_command).to be_a described_class
-      expect(subject.default_command.name).to eq 'get'
-    end
-  end
-
-  describe '#default_flags' do
-    let(:fixture) { :default_values }
-
-    it 'returns an array of only the Flags objects that have default' do
-      expect(subject.default_flags.size).to eq 1
-      expect(subject.default_flags.first.long).to eq '--format'
-    end
-  end
-
-  describe '#dependencies' do
-    let(:fixture) { :dependencies }
-
-    it 'returns an array of Dependency objects' do
-      expect(subject.dependencies).to be_an Array
-      expect(subject.dependencies.first).to be_a Script::Dependency
-    end
-  end
-
-  describe '#environment_cariables' do
-    it 'returns an array of EnvironmentVariable objects' do
-      expect(subject.environment_variables).to be_an Array
-      expect(subject.environment_variables.first).to be_a Script::EnvironmentVariable
-    end
-  end
-
-  describe '#examples' do
-    context 'when there are no examples' do
-      it 'returns nil' do
-        expect(subject.examples).to be_nil
-      end
-    end
-
-    context 'when there are examples as array' do
-      let(:fixture) { :examples_array }
-
-      it 'returns the array' do
-        expect(subject.examples).to be_an Array
-      end
-    end
-
-    context 'when there are examples as string' do
-      let(:fixture) { :examples_string }
-
-      it 'returns an array with one item' do
-        expect(subject.examples).to be_an Array
-        expect(subject.examples.count).to eq 1
-        expect(subject.examples.first).to start_with 'Download a file'
-      end
-    end
-  end
-
   describe '#filename' do
     context 'when it is the root command' do
       it 'returns root_command.sh' do
@@ -251,13 +121,6 @@
     end
   end
 
-  describe '#flags' do
-    it 'returns an array of Flag objects' do
-      expect(subject.flags).to be_an Array
-      expect(subject.flags.first).to be_a Script::Flag
-    end
-  end
-
   describe '#function_name' do
     let(:fixture) { :docker_container_run }
 
@@ -290,32 +153,6 @@
     end
   end
 
-  describe '#global_flags?' do
-    context 'when a command has flags and commands' do
-      let(:fixture) { :mode_global_flags }
-
-      it 'returns true' do
-        expect(subject).to be_global_flags
-      end
-    end
-
-    context 'when a command has flags but no commands' do
-      let(:fixture) { :mode_flags }
-
-      it 'returns false' do
-        expect(subject).not_to be_global_flags
-      end
-    end
-
-    context 'when a command has commands but no flags' do
-      let(:fixture) { :mode_commands }
-
-      it 'returns false' do
-        expect(subject).not_to be_global_flags
-      end
-    end
-  end
-
   describe '#group_string' do
     it 'returns a string suitable for showing the group in usage' do
       expect(subject.group_string).to eq 'Commands:'
@@ -330,16 +167,6 @@
     end
   end
 
-  describe '#grouped_commands' do
-    let(:fixture) { :exposed }
-
-    it 'returns a hash with an array of Command objects per group key' do
-      expect(subject.grouped_commands.keys).to contain_exactly('Cluster Commands:', 'Commands:')
-      expect(subject.grouped_commands['Commands:'].count).to eq 4
-      expect(subject.grouped_commands['Commands:']).to all(be_a described_class)
-    end
-  end
-
   describe '#has_unique_args_or_flags?' do
     context 'when the command has any args that are unique' do
       let(:fixture) { :unique_args }
@@ -455,69 +282,6 @@
     end
   end
 
-  describe '#needy_flags' do
-    let(:fixture) { :needy_flags }
-
-    it 'returns an array of only the needy Flag objects' do
-      expect(subject.needy_flags.size).to eq 2
-      expect(subject.needy_flags.first.long).to eq '--add'
-    end
-  end
-
-  describe '#public_commands' do
-    let(:fixture) { :private_commands }
-
-    it 'returns an array of Command objects excluding private commands' do
-      expect(subject.public_commands.count).to eq 1
-      expect(subject.public_commands.first.name).to eq 'connect'
-    end
-  end
-
-  describe '#public_commands_aliases' do
-    let(:fixture) { :private_commands }
-
-    it 'returns an array of command aliases of public subcommands' do
-      expect(subject.public_command_aliases).to eq %w[connect c]
-    end
-  end
-
-  describe '#required_args' do
-    it 'returns an array of only the required Argument objects' do
-      expect(subject.required_args.size).to eq 1
-      expect(subject.required_args.first.name).to eq 'source'
-    end
-  end
-
-  describe '#required_environment_variables' do
-    it 'returns an array of only the required Argument objects' do
-      expect(subject.required_environment_variables.size).to eq 1
-      expect(subject.required_environment_variables.first.name).to eq 'secret_key'
-    end
-  end
-
-  describe '#required_flags' do
-    it 'returns an array of only the required Flag objects' do
-      expect(subject.required_flags.size).to eq 1
-      expect(subject.required_flags.first.long).to eq '--force'
-    end
-  end
-
-  describe '#repeatable_arg_exist?' do
-    context 'when the command does not have any repeatable flags' do
-      it 'returns false' do
-        expect(subject.repeatable_arg_exist?).to be false
-      end
-    end
-
-    context 'when the command has at least one repeatable flag' do
-      let(:fixture) { :repeatable_arg }
-
-      it 'returns true' do
-        expect(subject.repeatable_arg_exist?).to be true
-      end
-    end
-  end
-
   describe '#root_command?' do
     context 'when the command has no parents' do
       it 'returns true' do
@@ -534,22 +298,6 @@
     end
   end
 
-  describe '#short_flag_exist?' do
-    let(:fixture) { :flag_hog }
-
-    context 'when the command has this short flag' do
-      it 'returns true' do
-        expect(subject.short_flag_exist?('-h')).to be true
-      end
-    end
-
-    context 'when the command does not have this short flag' do
-      it 'returns false' do
-        expect(subject.short_flag_exist?('-s')).to be false
-      end
-    end
-  end
-
   describe '#summary_string' do
     it 'returns the user defined summary' do
       expect(subject.summary_string).to eq 'get something from somewhere'
@@ -678,22 +426,4 @@
       end
     end
   end
-
-  describe '#whitelisted_args' do
-    let(:fixture) { :whitelist }
-
-    it 'returns an array of args that have a whitelist' do
-      expect(subject.whitelisted_args.size).to eq 1
-      expect(subject.whitelisted_args.first.name).to eq 'region'
-    end
-  end
-
-  describe '#whitelisted_flags' do
-    let(:fixture) { :whitelist }
-
-    it 'returns an array of flags that have a whitelist' do
-      expect(subject.whitelisted_flags.size).to eq 1
-      expect(subject.whitelisted_flags.first.long).to eq '--user'
-    end
-  end
 end
diff --git a/spec/bashly/script/introspection/arguments_spec.rb b/spec/bashly/script/introspection/arguments_spec.rb
new file mode 100644
index 00000000..d27c04c5
--- /dev/null
+++ b/spec/bashly/script/introspection/arguments_spec.rb
@@ -0,0 +1,58 @@
+describe Script::Introspection::Arguments do
+  subject do
+    result = Script::Command.new fixtures[fixture]
+    result.parents = result.options['parents']
+    result
+  end
+
+  let(:fixtures) { load_fixture 'script/commands' }
+  let(:fixture) { :basic_command }
+
+  describe '#args' do
+    it 'returns an array of Argument objects' do
+      expect(subject.args).to be_an Array
+      expect(subject.args.first).to be_a Script::Argument
+    end
+  end
+
+  describe '#default_args' do
+    let(:fixture) { :default_values }
+
+    it 'returns an array of only the Argument objects that have default' do
+      expect(subject.default_args.size).to eq 1
+      expect(subject.default_args.first.name).to eq 'files'
+    end
+  end
+
+  describe '#repeatable_arg_exist?' do
+    context 'when the command does not have any repeatable flags' do
+      it 'returns false' do
+        expect(subject.repeatable_arg_exist?).to be false
+      end
+    end
+
+    context 'when the command has at least one repeatable flag' do
+      let(:fixture) { :repeatable_arg }
+
+      it 'returns true' do
+        expect(subject.repeatable_arg_exist?).to be true
+      end
+    end
+  end
+
+  describe '#required_args' do
+    it 'returns an array of only the required Argument objects' do
+      expect(subject.required_args.size).to eq 1
+      expect(subject.required_args.first.name).to eq 'source'
+    end
+  end
+
+  describe '#whitelisted_args' do
+    let(:fixture) { :whitelist }
+
+    it 'returns an array of args that have a whitelist' do
+      expect(subject.whitelisted_args.size).to eq 1
+      expect(subject.whitelisted_args.first.name).to eq 'region'
+    end
+  end
+end
diff --git a/spec/bashly/script/introspection/commands_spec.rb b/spec/bashly/script/introspection/commands_spec.rb
new file mode 100644
index 00000000..9e9668d1
--- /dev/null
+++ b/spec/bashly/script/introspection/commands_spec.rb
@@ -0,0 +1,100 @@
+describe Script::Introspection::Commands do
+  subject do
+    result = Script::Command.new fixtures[fixture]
+    result.parents = result.options['parents']
+    result
+  end
+
+  let(:fixtures) { load_fixture 'script/commands' }
+  let(:fixture) { :basic_command }
+
+  describe '#command_aliases' do
+    let(:fixture) { :aliases }
+
+    it 'returns an array of command aliases' do
+      expect(subject.command_aliases).to eq %w[download d pull upload u push update upgrade]
+    end
+  end
+
+  describe '#command_help_data' do
+    let(:fixture) { :exposed }
+
+    it 'returns a hash suitable for showing command and exposed subcommand help' do
+      expect(subject.command_help_data.to_yaml)
+        .to match_approval('script/command/exposed_commands')
+    end
+  end
+
+  describe '#command_names' do
+    let(:fixture) { :docker }
+
+    it 'returns an array of command names' do
+      expect(subject.command_names).to eq %w[container image]
+    end
+  end
+
+  describe '#commands' do
+    let(:fixture) { :docker }
+
+    it 'returns an array of Command objects' do
+      expect(subject.commands).to be_an Array
+      expect(subject.commands.first).to be_a described_class
+    end
+
+    it 'sets the parents property of its commands' do
+      expect(subject.commands.first.parents).to eq ['docker']
+    end
+  end
+
+  describe '#deep_commands' do
+    let(:fixture) { :docker }
+
+    it 'returns an array of all commands in the tree' do
+      expect(subject.deep_commands.map(&:full_name))
+        .to eq ['docker container', 'docker container run', 'docker container stop', 'docker image']
+    end
+
+    context 'when include_self is true' do
+      it 'prepends the result with the command itself' do
+        expect(subject.deep_commands(include_self: true).map(&:full_name))
+          .to eq ['docker', 'docker container', 'docker container run', 'docker container stop', 'docker image']
+      end
+    end
+  end
+
+  describe '#default_command' do
+    let(:fixture) { :default_command }
+
+    it 'returns a Command object of the first default command' do
+      expect(subject.default_command).to be_a described_class
+      expect(subject.default_command.name).to eq 'get'
+    end
+  end
+
+  describe '#grouped_commands' do
+    let(:fixture) { :exposed }
+
+    it 'returns a hash with an array of Command objects per group key' do
+      expect(subject.grouped_commands.keys).to contain_exactly('Cluster Commands:', 'Commands:')
+      expect(subject.grouped_commands['Commands:'].count).to eq 4
+      expect(subject.grouped_commands['Commands:']).to all(be_a described_class)
+    end
+  end
+
+  describe '#public_commands' do
+    let(:fixture) { :private_commands }
+
+    it 'returns an array of Command objects excluding private commands' do
+      expect(subject.public_commands.count).to eq 1
+      expect(subject.public_commands.first.name).to eq 'connect'
+    end
+  end
+
+  describe '#public_commands_aliases' do
+    let(:fixture) { :private_commands }
+
+    it 'returns an array of command aliases of public subcommands' do
+      expect(subject.public_command_aliases).to eq %w[connect c]
+    end
+  end
+end
diff --git a/spec/bashly/script/introspection/dependencies_spec.rb b/spec/bashly/script/introspection/dependencies_spec.rb
new file mode 100644
index 00000000..389de2a8
--- /dev/null
+++ b/spec/bashly/script/introspection/dependencies_spec.rb
@@ -0,0 +1,19 @@
+describe Script::Introspection::Dependencies do
+  subject do
+    result = Script::Command.new fixtures[fixture]
+    result.parents = result.options['parents']
+    result
+  end
+
+  let(:fixtures) { load_fixture 'script/commands' }
+  let(:fixture) { :basic_command }
+
+  describe '#dependencies' do
+    let(:fixture) { :dependencies }
+
+    it 'returns an array of Dependency objects' do
+      expect(subject.dependencies).to be_an Array
+      expect(subject.dependencies.first).to be_a Script::Dependency
+    end
+  end
+end
diff --git a/spec/bashly/script/introspection/environment_variables_spec.rb b/spec/bashly/script/introspection/environment_variables_spec.rb
new file mode 100644
index 00000000..a400676c
--- /dev/null
+++ b/spec/bashly/script/introspection/environment_variables_spec.rb
@@ -0,0 +1,52 @@
+describe Script::Introspection::EnvironmentVariables do
+  subject do
+    result = Script::Command.new fixtures[fixture]
+    result.parents = result.options['parents']
+    result
+  end
+
+  let(:fixtures) { load_fixture 'script/commands' }
+  let(:fixture) { :environment_variable_enthusiast }
+
+  describe '#default_environment_variables' do
+    it 'returns an array of all the Environment Variables with default values' do
+      expect(subject.default_environment_variables.size).to eq 1
+      expect(subject.default_environment_variables.first.name).to eq 'file'
+    end
+  end
+
+  describe '#environment_variables' do
+    it 'returns an array of EnvironmentVariable objects' do
+      expect(subject.environment_variables).to be_an Array
+      expect(subject.environment_variables).to all(be_a Script::EnvironmentVariable)
+    end
+  end
+
+  describe '#public_environment_variables' do
+    it 'returns only environment variables that are not private' do
+      expect(subject.public_environment_variables.size).to eq 4
+      expect(subject.public_environment_variables.map(&:name)).not_to include 'secret'
+    end
+  end
+
+  describe '#required_environment_variables' do
+    it 'returns an array of only the required Argument objects' do
+      expect(subject.required_environment_variables.size).to eq 1
+      expect(subject.required_environment_variables.first.name).to eq 'username'
+    end
+  end
+
+  describe '#validated_environment_variables' do
+    it 'returns an array of all the environment variables with a validation' do
+      expect(subject.validated_environment_variables.size).to eq 1
+      expect(subject.validated_environment_variables.first.name).to eq 'config_dir'
+    end
+  end
+
+  describe '#whitelisted_environment_variables' do
+    it 'returns an array of all the environment_variables with a whitelist arg' do
+      expect(subject.whitelisted_environment_variables.size).to eq 1
+      expect(subject.whitelisted_environment_variables.first.name).to eq 'protocol'
+    end
+  end
+end
diff --git a/spec/bashly/script/introspection/examples_spec.rb b/spec/bashly/script/introspection/examples_spec.rb
new file mode 100644
index 00000000..ab08c068
--- /dev/null
+++ b/spec/bashly/script/introspection/examples_spec.rb
@@ -0,0 +1,36 @@
+describe Script::Introspection::Examples do
+  subject do
+    result = Script::Command.new fixtures[fixture]
+    result.parents = result.options['parents']
+    result
+  end
+
+  let(:fixtures) { load_fixture 'script/commands' }
+  let(:fixture) { :basic_command }
+
+  describe '#examples' do
+    context 'when there are no examples' do
+      it 'returns nil' do
+        expect(subject.examples).to be_nil
+      end
+    end
+
+    context 'when there are examples as array' do
+      let(:fixture) { :examples_array }
+
+      it 'returns the array' do
+        expect(subject.examples).to be_an Array
+      end
+    end
+
+    context 'when there are examples as string' do
+      let(:fixture) { :examples_string }
+
+      it 'returns an array with one item' do
+        expect(subject.examples).to be_an Array
+        expect(subject.examples.count).to eq 1
+        expect(subject.examples.first).to start_with 'Download a file'
+      end
+    end
+  end
+end
diff --git a/spec/bashly/script/introspection/flags_spec.rb b/spec/bashly/script/introspection/flags_spec.rb
new file mode 100644
index 00000000..bdef65b1
--- /dev/null
+++ b/spec/bashly/script/introspection/flags_spec.rb
@@ -0,0 +1,102 @@
+describe Script::Introspection::Flags do
+  subject do
+    result = Script::Command.new fixtures[fixture]
+    result.parents = result.options['parents']
+    result
+  end
+
+  let(:fixtures) { load_fixture 'script/commands' }
+  let(:fixture) { :basic_command }
+
+  describe '#default_flags' do
+    let(:fixture) { :default_values }
+
+    it 'returns an array of only the Flags objects that have default' do
+      expect(subject.default_flags.size).to eq 1
+      expect(subject.default_flags.first.long).to eq '--format'
+    end
+  end
+
+  describe '#flags' do
+    it 'returns an array of Flag objects' do
+      expect(subject.flags).to be_an Array
+      expect(subject.flags.first).to be_a Script::Flag
+    end
+  end
+
+  describe '#global_flags?' do
+    context 'when a command has flags and commands' do
+      let(:fixture) { :mode_global_flags }
+
+      it 'returns true' do
+        expect(subject).to be_global_flags
+      end
+    end
+
+    context 'when a command has flags but no commands' do
+      let(:fixture) { :mode_flags }
+
+      it 'returns false' do
+        expect(subject).not_to be_global_flags
+      end
+    end
+
+    context 'when a command has commands but no flags' do
+      let(:fixture) { :mode_commands }
+
+      it 'returns false' do
+        expect(subject).not_to be_global_flags
+      end
+    end
+  end
+
+  describe '#needy_flags' do
+    let(:fixture) { :needy_flags }
+
+    it 'returns an array of only the needy Flag objects' do
+      expect(subject.needy_flags.size).to eq 2
+      expect(subject.needy_flags.first.long).to eq '--add'
+    end
+  end
+
+  describe '#public_flags' do
+    let(:fixture) { :private_flags }
+
+    it 'returns an array of only the non private Flag objects' do
+      expect(subject.public_flags.size).to eq 1
+      expect(subject.public_flags.first.long).to eq '--new'
+    end
+  end
+
+  describe '#required_flags' do
+    it 'returns an array of only the required Flag objects' do
+      expect(subject.required_flags.size).to eq 1
+      expect(subject.required_flags.first.long).to eq '--force'
+    end
+  end
+
+  describe '#short_flag_exist?' do
+    let(:fixture) { :flag_hog }
+
+    context 'when the command has this short flag' do
+      it 'returns true' do
+        expect(subject.short_flag_exist?('-h')).to be true
+      end
+    end
+
+    context 'when the command does not have this short flag' do
+      it 'returns false' do
+        expect(subject.short_flag_exist?('-s')).to be false
+      end
+    end
+  end
+
+  describe '#whitelisted_flags' do
+    let(:fixture) { :whitelist }
+
+    it 'returns an array of flags that have a whitelist' do
+      expect(subject.whitelisted_flags.size).to eq 1
+      expect(subject.whitelisted_flags.first.long).to eq '--user'
+    end
+  end
+end
diff --git a/spec/fixtures/script/commands.yml b/spec/fixtures/script/commands.yml
index b4c49077..50a9c427 100644
--- a/spec/fixtures/script/commands.yml
+++ b/spec/fixtures/script/commands.yml
@@ -199,6 +199,20 @@
   help: perform docker container run
   parents: [docker, container]
 
+:environment_variable_enthusiast:
+  name: get
+  environment_variables:
+  - name: username
+    required: true
+  - name: file
+    default: README.md
+  - name: config_dir
+    validate: dir_exists
+  - name: protocol
+    allowed: [ssh, https]
+  - name: secret
+    private: true
+
 :examples_array:
   name: get
   help: get something from somewhere
@@ -404,6 +418,14 @@
     alias: cf
     private: true
 
+:private_flags:
+  name: status
+  help: perform git status
+  flags:
+  - long: --legacy
+    private: true
+  - long: --new
+
 :repeatable_arg:
   name: get
   args:
diff --git a/support/schema/bashly.yml b/support/schema/bashly.yml
index 70ac28a6..37fd6a01 100644
--- a/support/schema/bashly.yml
+++ b/support/schema/bashly.yml
@@ -300,6 +300,17 @@ definitions:
           https://bashly.dannyb.co/configuration/environment-variable/#required
         type: boolean
         default: true
+      validate:
+        title: validate
+        description: |-
+          A validation function for the current environment variable
+          https://bashly.dannyb.co/configuration/environment-variable/#validate
+        type: string
+        examples:
+          - file_exists
+          - dir_exists
+          - integer
+          - non_empty
       allowed:
         title: allowed
         description: |-