add is_starting callback in builder (experimental)

lib/container.ex

@@ -146,5 +146,9 @@ defmodule Testcontainers.Container do
     def build(%Testcontainers.Container{} = config) do
       config
     end
+
+    @impl true
+    @spec is_starting(%Testcontainers.Container{}, %Testcontainers.Container{}) :: any()
+    def is_starting(_config, _container), do: nil
   end
 end

lib/container/cassandra_container.ex

@@ -80,5 +80,9 @@ defmodule Testcontainers.CassandraContainer do
         )
       )
     end
+
+    @impl true
+    @spec is_starting(%CassandraContainer{}, %Container{}) :: any()
+    def is_starting(_config, _container), do: nil
   end
 end

lib/container/ceph_container.ex

@@ -230,6 +230,10 @@ defmodule Testcontainers.CephContainer do
         )
       )
     end
+
+    @impl true
+    @spec is_starting(%CephContainer{}, %Container{}) :: any()
+    def is_starting(_config, _container), do: nil
   end
 end
 

lib/container/minio_container.ex

@@ -74,5 +74,9 @@ defmodule Testcontainers.MinioContainer do
         LogWaitStrategy.new(~r/.*Status:         1 Online, 0 Offline..*/, config.wait_timeout)
       )
     end
+
+    @impl true
+    @spec is_starting(%MinioContainer{}, %Container{}) :: any()
+    def is_starting(_config, _container), do: nil
   end
 end

lib/container/mysql_container.ex

@@ -205,6 +205,10 @@ defmodule Testcontainers.MySqlContainer do
         LogWaitStrategy.new(~r/.*port: 3306  MySQL Community Server.*/, config.wait_timeout)
       )
     end
+
+    @impl true
+    @spec is_starting(%MySqlContainer{}, %Container{}) :: any()
+    def is_starting(_config, _container), do: nil
   end
 
   @doc false

lib/container/postgres_container.ex

@@ -211,6 +211,10 @@ defmodule Testcontainers.PostgresContainer do
         )
       )
     end
+
+    @impl true
+    @spec is_starting(%PostgresContainer{}, %Container{}) :: any()
+    def is_starting(_config, _container), do: nil
   end
 
   @doc false

lib/container/protocols/container_builder.ex

@@ -4,4 +4,7 @@ defprotocol Testcontainers.ContainerBuilder do
   """
   @spec build(t()) :: %Testcontainers.Container{}
   def build(builder)
+
+  @spec is_starting(t(), %Testcontainers.Container{}) :: any()
+  def is_starting(builder, container)
 end

lib/container/redis_container.ex

@@ -139,6 +139,10 @@ defmodule Testcontainers.RedisContainer do
         CommandWaitStrategy.new(["redis-cli", "PING"], config.wait_timeout)
       )
     end
+
+    @impl true
+    @spec is_starting(%RedisContainer{}, %Container{}) :: any()
+    def is_starting(_config, _container), do: nil
   end
 end
 

lib/container/selenium_container.ex

@@ -68,6 +68,10 @@ defmodule Testcontainers.SeleniumContainer do
         PortWaitStrategy.new("127.0.0.1", config.port2, config.wait_timeout, 1000)
       ])
     end
+
+    @impl true
+    @spec is_starting(%SeleniumContainer{}, %Container{}) :: any()
+    def is_starting(_config, _container), do: nil
   end
 end
 

lib/testcontainers.ex

@@ -215,6 +215,7 @@ defmodule Testcontainers do
          {:ok, id} <- Api.create_container(config, state.conn),
          :ok <- Api.start_container(id, state.conn),
          {:ok, container} <- Api.get_container(id, state.conn),
+         _ <- ContainerBuilder.is_starting(config, container),
          :ok <- wait_for_container(container, config.wait_strategies || [], state.conn) do
       {:ok, container}
     end